Session diagnostics error

Hi Matthew_Martell​,
Thanks for confirming that the issue also occurs in the August 2026 release.

Microsoft’s documentation explains that Start Diagnostics records evaluations triggered during actions such as Refresh Preview, while Diagnose Step performs a separate evaluation for the selected step. 

Since the "0x80131623" error persists when using Start Diagnostics -> Refresh Preview, I recommend reaching out to Microsoft Support for further investigation. You can provide them with the affected Power BI Desktop versions, the error code, and the observations already confirmed in this thread.

You can submit a support request from Power BI Desktop -> Help -> Support -> Submit a ticket, or use the Microsoft Learn link below:
Create a Fabric and Power BI Support Ticket - Power BI | Microsoft Learn

For more details, please refer to the below Official Microsoft Documentation:
Query diagnostics - Power Query | Microsoft Learn
Record Query Diagnostics in Power BI - Power Query | Microsoft Learn

I hope this helps. Please feel free to reach out if you have any further questions.
Thank you.