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Trouble Updating Lookup Column Power Automate, Error 404

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Posted on by SD-10041658-0

I have a table called Budget Report, with an empty lookup column to the table Financial Record. I am trying to update the empty lookup column in Budget Report with identical values from another column in the table (the original lookup column in Excel, since microsoft power apps makes you remake the lookup column when importing tables). I have been able to accurately get the required row GUID and the value I want to update, but Power Automate keeps giving me a Not Found error. Is there an error somewhere in my syntax? Here is my whole flow:

The first compose (Compose 1) is simply putting the values from List Rows into an array, since it returns me a list of tables. The second compose (Compose 2) is to get the GUID, which is 'crfbf_budgetreportid.' My Compose 2 is written dynamically as follows:

first(outputs('Compose'))?['crfbf_budgetreportid']

The third compose (Compose 3) is to get the string I want to actually put in the updated column. This is called the chartstring, and my Compose 3 is written as follows:

first(outputs('Compose'))?['crfbf_chartstring']

Then we get to trying to update the row. Because my GUID comes from the table I am trying to update, Budget Report, in Row ID I put

/crfbf_budgetreports(Outputs('Compose 2'))

making sure to sue the correct PluralEntity name. This should work, as Outputs('Compose 2') just gives me the string GUID of the row.

The actual column I am trying to update is called "chartstring_lookup2(Financial Record)", and is the lookup column from Budget Report to Financial Record. For that value I put in

/crfbf_financial(Outputs('Compose 3'))

because Outputs('Compose 3') directly gives me the string I am trying to put in the lookup column.

Here is what my Update a Row block looks like:

Here is the Update block

However when I run my flow I get a 404 error message, like so:

<h2>404 - File or directory not found. </h2> <h3>The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable. </h3>

I am not sure where my issue is, as I can't tell if the 404 is because of the Row ID or the actual lookup column I am trying to update. I am very sure my Row ID input is correct, as I have compared it with many online sources. I think my issue comes in how I am updating the row itself, but I don't know how else to format it. Should I not be using the PluralEntityName of the lookup table, crfbf_financialrecords, before? Should I use the PluralEntityName of the table i am updating, crfbf_budgetreports? Do I even need the PluralEntityName for that part, or can I just put in the chartstring output from Compose 3 by itself?

I have tried these methods I just listed but then Power Automate doesn't fully save my changes, so I don't know if it's still not working because of me or if the system is just glitching. Any insight or help would be greatly appreciated!

p.s. I am adding my code screenshots as attachments just in case the images don't show in the actual post, since I can't see them in the editor.

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Dynamics 365 general

Power Platform integration

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Holly Huffman 6,538 Super User 2025 Season 2 on at

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Good morning, afternoon, or evening :) depending on your location!

The 404 error in Power Automate typically indicates that the resource being referenced (e.g., Row ID or lookup column) cannot be found or accessed. Based on your description, here are some steps to troubleshoot and resolve the issue:
Key Areas to Verify:

Row ID Syntax:
Ensure that the Row ID is formatted correctly. The syntax should be:
crfbf_budgetreports(Outputs('Compose 2'))

Avoid including a leading slash (/) in the Row ID field, as Power Automate automatically handles the URL structure.

Lookup Column Value:
For the lookup column chartstring_lookup2(Financial Record), the value should reference the GUID of the related record in the Financial Record table. The correct syntax is:
crfbf_financialrecords(Outputs('Compose 3'))

Again, avoid using a leading slash (/) in this field.

Plural Entity Names:
Verify that you are using the correct plural entity names for both tables (Budget Report and Financial Record). You can find these names in the Dataverse table settings under "Entity Set Name."

GUID Validation:
Confirm that the GUIDs retrieved in Compose 2 and Compose 3 are valid and exist in their respective tables. You can test this by querying the Dataverse API or using a tool like Postman.

Permissions:
Ensure that the connection being used in Power Automate has sufficient permissions to update the Budget Report table and access the Financial Record table.

Additional Suggestions:

Test with Static Values:
Replace the dynamic values in the Row ID and lookup column fields with static GUIDs to test if the issue is with the dynamic expressions.

Check for Hidden Characters:
Sometimes, hidden characters or formatting issues in the expressions can cause errors. Re-enter the expressions manually to ensure they are clean.

Enable Debugging:
Add a "Compose" action before the Update a Row step to output the exact values being passed to the Row ID and lookup column fields. This can help identify any discrepancies.

Example Update Block Configuration:
Here’s how your Update a Row block should look:

Row ID:
crfbf_budgetreports(Outputs('Compose 2'))

chartstring_lookup2(Financial Record):
crfbf_financialrecords(Outputs('Compose 3'))

Hope this helps!

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Anne Pessoa 14 on at

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Hi,

Building lookup references by hand in power automate can sometimes get a bit tricky, have you tried the Dataverse REST Builder? You can either use the XrmToolbox plugin, install the solution in your environment and run it from there or use a browser extension. This should help you build the request with the correct syntax.

https://github.com/GuidoPreite/DRB

Hope it helps,

Anne Pessoa.

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Tom_Gioielli 2,797 Super User 2025 Season 2 on at

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I'm having a little trouble following your compose actions, but that's likely because it's late where I am. Regardless, we should be able to figure this out without getting too deep into it.

When setting a lookup field in Dataverse through Power Automate, you look to be on the right track.

The pluralset name of the table you are pointing to should be used (in this case I believe that is crfbf_financialrecords)

You need the GUID of the record you are pointing to

You need the GUID of the record to be updated (along with finding the table name in the dropdown).

Based on your screenshots, I know you have one problem (there might be a second problem, but I don't think it has a huge impact).

ISSUE 1

Your Row ID in the update action is incorrect. Because you are already defining the table you are going to be updating a record within (Budget Report), the Row ID does not need to define the table. This value should simply be the GUID of the record you are updating.

Resolution: Remove the below section and only use the GUID of your record to update.
/crfbf_budgetreports()

ISSUE 2 (maybe?)

When setting the lookup field value, I usually don't do a '/' before the table pluralset name. I don't know that this would actually cause an issue, but it's possible. If you fix issue 1 above and you still run into an error, try removing that.

My recommendation when learning Power Automate and doing these actions is to first try it with some hard coded values when you run into trouble. Grab a record GUID and a lookup record GUID, and just paste them directly into where you have your Compose variables. Then test the flow and make sure the records update as expected. Once you've done that, you know your syntax is correct and all you need to do is update the hard-coded values with your variable.

Honestly, you're super close, and this is a pretty common mistake and learning experience. AI responses that say to include the pluralset name in the Row ID also don't help the situation, so just ignore those. Let me know if it works, or if you run into any further issues and I'll do what I can to help.

If this answer helped, please consider marking as verified.

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