Need help with Power Automate Custom Connector & On-Premises API Integration

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Posted on by irfanbcitian

I have an on-premises POST API hosted on an Azure VM. I'm trying to call this API from a Power Automate flow using a Custom Connector and On-Premises Data Gateway.
🔧 The API is accessible locally via localhost, and I've configured the connector accordingly with the gateway.
However, when I test the Custom Connector, I consistently receive the following error:
"Request failed. Please try again in a few minutes."
📌 Additional Notes:
The API works perfectly in Postman.
Service Tags have been assigned as per the region of Power Automate.
The gateway is online and appears under my environment.
Has anyone faced a similar issue or have insights on what might be missing?
Appreciate any guidance or suggestions 🙏

Please note: I am following the same step as defined in the blog
https://www.microsoft.com/en-us/power-platform/blog/power-automate/on-premise-apis/

Categories:

Dynamics 365 general

Power Platform integration

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Holly Huffman 6,554 Super User 2026 Season 1 on at

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Good morning, afternoon, or evening depending on your location :)
Hope you are well today!

Thanks for sharing the screenshot—it confirms that you're encountering the "Request failed. Please try again in a few minutes." error on the Test tab of the Power Automate Custom Connector interface.
Here’s what this tells us and how to proceed:

What the Screenshot Confirms

You're testing the connector from the “Test” tab in the Power Automate UI.

The error is generic and doesn’t provide detailed diagnostics.

This is a known limitation: the Test tab often fails when using On-Premises Data Gateway or custom authentication, even if the connector works in a real flow.

Recommended Next Steps
1. Test the Connector in a Real Flow

Create a simple Power Automate flow that uses the custom connector.

Add a manual trigger and call the connector action.

Check the flow run history for detailed error messages.

This often bypasses the limitations of the Test tab and gives better diagnostics.

2. Check Gateway Logs

On the machine hosting the On-Premises Data Gateway, check logs at:

C:\Program Files\On-premises data gateway\GatewayLogs

Look for entries around the time of your test to identify connection or authentication issues.

3. Update the Base URL

In the Custom Connector, ensure the host URL is not localhost.

Use the internal IP address or DNS name of the Azure VM.

Example: http://10.0.0.4:5000/api/endpoint

4. Check Authentication Settings

If your API requires authentication (e.g., API key, Basic Auth), ensure:

The security tab in the connector is configured correctly.

The test call includes the required headers or tokens.

Note: I collaborated with Copilot to help craft this response for clarity and completeness.
Hope this helps some!

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