Intermittent 400 Error with Power BI Desktop - ODBC Connection to SQL Warehouse

[rajanator]

Hi all,

I'm experiencing an intermittent connection issue between Power BI Desktop and our Azure Databricks SQL Warehouse and looking for help troubleshooting

Error Message:
ODBC: ERROR [HY000] [Microsoft][ThriftExtension] (14) Unexpected response from server during a HTTP connection: Bad Status: Unrecognized response with no error message header. Status code: 400.

Setup:

• Connection: Azure Databricks SQL Warehouse via ODBC
• Client: Power BI Desktop (latest October 2025 version)
• Authentication: Azure AD / Organizational account
• All queries use Value.NativeQuery() with native SQL

Behaviour:

• Error occurs randomly - no consistent pattern
• Affects ALL Databricks queries in the model (10+ tables)
• SQL Warehouse status is "Running" when error occurs
• Occurs even in brand new Power BI files

Started after a failed connection attempt while working from home one day (was not aware at the time that org does not allow azure databricks connection while working for home)

What temporarily fixes it:

• Clearing credentials in Power BI Data Source Settings
• But the error returns randomly (hours or days later)

Already tried:

• Verified SQL Warehouse is running before refresh
• Cleared Power BI data source credentials multiple times
• Removed cached Azure credentials from Windows Credential Manager
• Tested with Implementation parameter set to null/default
• Added ConnectionTimeout and CommandTimeout parameters
• Created brand new Power BI file from scratch - same issue

Running out of troubleshooting options. 

[mark_ott]

The intermittent ODBC error you’re seeing in Power BI when connecting to Azure Databricks is a recognized issue related to SSL validation interruptions or proxy interference in the Simba ThriftExtension layer. The behavior—random occurrences, temporary resolution by clearing credentials, and the recent start after remote access—strongly points to a network trust or authentication token caching issue.

Root Causes

Recent Microsoft and Databricks discussions identify several common triggers:

• SSL/Certificate verification failure caused by corporate proxy inspection or firewall rewriting the Databricks SSL certificate (e.g., Zscaler, Palo Alto, or Windows Defender MITM scanning).​

• Corrupted cached Azure AD tokens in Power BI after a failed offsite (VPN or remote) authentication attempt.​

• Firewall or conditional access blocks when Power BI attempts automatic token refresh in the background.​

• ODBC driver instability introduced in mid-2025 Power BI Desktop releases (Simba Spark ODBC driver component).​

Recommended Fixes

1. Disable revocation checking (test only)

   • Navigate to
     C:\Program Files\Microsoft Power BI Desktop\bin\ODBC Drivers\Simba Spark ODBC Driver\

   • Create or edit a file named microsoft.sparkodbc.ini

   • Add:

     text

     [Driver] CheckCertRevocation=0

   • Save, restart Power BI Desktop, then retest.​

2. Add your corporate SSL inspection certificate

   • Obtain the organization’s root or intermediate CA certificate (e.g., from Zscaler or Palo Alto) in .pem or .crt format.

   • Append it to the ODBC driver’s trust store in the same directory as above.​

3. Force Power BI to reissue authentication tokens

   • In Power BI Desktop, open File → Options and Settings → Data Source Settings → Edit Permissions.

   • Select the Databricks entry, then Clear Permissions and sign in again using Azure Active Directory.

   • Ensure no credentials for Databricks remain in Windows Credential Manager.

4. Network enforcement

   • If your org disallows Databricks connections from non-corporate networks, cached credentials created from a home IP can poison future refresh attempts. Restarting Power BI on a whitelisted network and reauthenticating resolves this.​

5. Optional mitigation

   • Update to the most recent Power BI Desktop patch (October 2025 hotfix includes connection stability improvements for Databricks private-link environments).​

   • If instability persists, test using the Direct Databricks connector (not ODBC) via the Azure Databricks option within Power BI Get Data; it uses the REST interface rather than Thrift.​

Summary

The ODBC [HY000] ThriftExtension 400/SSL-related error occurs because Power BI’s embedded Simba ODBC driver intermittently fails SSL or token validation, often due to network inspection or corrupted cached credentials. Applying the certificate update or adjusting revocation settings has resolved this for most users on current builds