Dynamics Community Forum Thread Details

VS 2019 SSRS + Dynamics365 FetchXML: Dataset preview fails. “Unable to connect to data source"

I’m developing SSRS reports for Dynamics 365 (Dataverse) in Visual Studio 2019, using the following developer‑tooling setup:

Visual Studio 2019 (16.x)
Microsoft Reporting Services Projects extension
Dynamics 365 Report Authoring Extension
FetchXML datasets via Microsoft Dynamics 365 Fetch data source

This tooling has worked for years, but now the SSRS designer in VS2019 cannot Refresh Fields or Preview datasets, which blocks report development.

Steps to reproduce

Open an existing Report Server Project (RDLs using FetchXML datasets) in Visual Studio 2019.
In Report Data, right‑click a dataset → Query… → Refresh Fields or attempt Preview.
Sign‑in prompt may appear (sometimes it doesn’t).
Operation fails.

This is a failure inside Visual Studio’s SSRS designer, not on the report server.

Error messages

Visual Studio error dialog:

Unable to connect to data source 'DataSource1'.
The connection to server "https://<org>.crm.dynamics.com" could not be established.
Make sure that the connection string and credentials are correct, and try again.

Log file (from the CrmConnection login error log):
- C:\Users\{Login}\AppData\Roaming\Microsoft Corporation\Microsoft® Visual Studio®\16.7.32413.119\Login_ErrorLog.log
```
Error : The authentication type must be specified.
Parameter name: CrmPassword
```

What I’ve tried (tooling‑specific)

Re‑entering credentials / different accounts / device code sign‑in
Verified the Dynamics 365 Fetch datasource configuration
Tried repairing / reinstalling:
- Reporting Services Projects extension
- Dynamics 365 Report Authoring Extension
- Complete uninstall and reinstall of Visual Studio 2019
Clearing temp folders under %LOCALAPPDATA% related to VS/SSRS
Creating a brand‑new Report Server Project and a simple FetchXML dataset

Same result across machines: preview/refresh fails with the auth error.

Expected vs. actual

Expected: The SSRS designer in VS2019 should authenticate to Dataverse and allow dataset Refresh/Preview.
Actual: Fails with the error above.

What causes this Visual Studio 2019 SSRS designer failure when using the Dynamics 365 FetchXML data source, and what developer‑side fix restores normal dataset Refresh/Preview?

FOUND THE SOLUTION

Close Visual Studio.
Delete the contents of this folder (do not skip):
- %APPDATA%\Microsoft\PreviewProcessingService
- (e.g., C:\Users\<you>\AppData\Roaming\Microsoft\PreviewProcessingService)
Optional: If Default_PreviewProcessingService.exe is running, end the process (it will be recreated).
Reopen your Report Server Project and refresh the dataset/preview again.

This resets the local preview host that SSRS uses inside VS and clears the bad state that breaks modern auth to Dataverse/CRM. No reinstall required.
Notes / Context

You still need the Microsoft Reporting Services Projects extension + Dynamics 365 Report Authoring Extension for VS 2019; 2022 isn’t fully supported for this workflow yet, so stick with VS 2019.
If setup is incomplete (tooling missing), see Microsoft Q&A guidance on getting D365 tooling working with VS 2019.

TL;DR:

When D365 SSRS previews suddenly start failing in VS2019 with an auth error, clear %APPDATA%\Microsoft\PreviewProcessingService and restart VS. This has restored preview/refresh reliably.

Categories:

Dynamics 365 general

Power Platform integration

I wanted to share the solution to the problem to prevent anyone else from wasting 2 days.

THE SOLUTION

Close Visual Studio.
Delete the contents of this folder (do not skip):
- %APPDATA%\Microsoft\PreviewProcessingService
- (e.g., C:\Users\<yourlogin>\AppData\Roaming\Microsoft\PreviewProcessingService)
Optional: If Default_PreviewProcessingService.exe is running, end the process (it will be recreated).
Reopen your Report Server Project and refresh the dataset/preview again.

This resets the local preview host that SSRS uses inside VS and clears the bad state that breaks modern auth to Dataverse/CRM. No reinstall required.
Notes / Context

TL;DR:

When D365 SSRS previews suddenly start failing in VS2019 with an auth error, clear %APPDATA%\Microsoft\PreviewProcessingService and restart VS. This has restored preview/refresh reliably.

Quick Links

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