Google Big Query Connector - May 25 Release

Hi Dilbertfan, 

Thank you for reaching out to the Microsoft fabric community forum. Also, thanks Akash_Varuna, for those valuable insights for this thread. I have identified several alternative workarounds that may assist in resolving the thread.

Based on the error you're encountering:
ADBC: Status(StatusCode="Internal", Detail="Bad gRPC response. Response protocol downgraded to HTTP/1.1"),

This relates to the newly introduced Google Big Query connector using ADBC, which was released in Power BI Desktop’s May 2025 update and is currently in Preview. The ADBC-based connector utilizes gRPC over HTTP/2, providing enhanced performance and modern protocol advantages. However, it requires network environments that support HTTP/2. The error suggests that gRPC is reverting to HTTP/1.1, which the new connector does not support, resulting in the failure.

As the connector is currently in Preview, you may option to use the legacy version:

• Go to File > Options and settings > Options > Preview Features
• Uncheck: "Use ADBC-based Big Query connector"
• Restart Power BI Desktop
• This will revert to the previous (ODBC-based) connector, which does not rely on HTTP/2.

 If continuing with the Preview connector: Please ensure the following network conditions: HTTP/2 support is enabled end-to-end. No TLS/SSL inspection or proxy is downgrading HTTP/2 to HTTP/1.1

Whitelist the following domains:

• *.googleapis.com
• bigquery.googleapis.com
• oauth2.googleapis.com

These changes may require assistance from your IT/network team.

Kindly please refer to the below mentioned link for better understanding and more information:
Google Big Query connector - Power Query | Microsoft Learn
Compare gRPC services with HTTP APIs | Microsoft Learn

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