Issue with external API call in Copilot Studio

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Posted on by MF-17121103-0

Hi all,

I'm calling a simple external GET API from the native HTTP action in Copilot Studio / Power Automate, and it keeps failing with this error:

"BadRequest. Http request failed as there is an error: 'The server returned status code 500 when status code 101 was expected. (mydomain.com:443)'"

Details:
- Method: GET
- Just one header (an auth token)
- No query params, no body
- The exact same request works perfectly in Postman (same URL, same header, same token)

What I've already checked/ruled out:
- Payload/headers are correct (confirmed identical to the working Postman request)
- No DLP (Data Loss Prevention) policy is blocking this connector or domain
- No IP allowlisting issue on the API server side (confirmed with the team that manages it)

This was working fine before and just recently started failing.

Categories:

Calling actions from Copilot Studio

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Haque 3,728 on at

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Hi @MF-17121103-0,

Let's identify first what 101 response is: The 101 status code in HTTP is defined as Switching Protocols. It’s an informational response that indicates the server understands and agrees to switch to another protocol, as requested by the client through the Upgrade header field. Refernce is here.

And obvisouly, we see 500 becuase it received a unexpected request format or headers from PA. Pouwer Automate HTTP action was expecting like 200 and saw 100 - which is not supported as upgrades protocol.

As it was working earlier - The first thing I suspect is the API server or its config may have changed to require or expect protocol upgrade headers. Can you please review the latest API documentation or contact API provider to confirm if the end point expects something different like WebSocket or HTTP upgrades headers? If yes, Power Automate HTTP action cannot handle this natively.

I am sure some clues I tried to give. If these clues help to resolve the issue brought you by here, please don't forget to check the box Does this answer your question? At the same time, I am pretty sure you have liked the response!

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11manish 3,491 on at

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Based on the symptoms, the problem is most likely not related to the GET request itself, but to either:

A recent change on the API server or gateway causing protocol negotiation to fail, or

A recent change in the Power Platform HTTP connector affecting how the connection is established.

If the API team confirms that no server-side changes have been made and the server logs don't reveal the cause, I recommend opening a Microsoft support ticket

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