I have a flow that starts when a file is created in my Onedrive for Business. The flow worked before, but it suddenly stopped.
Below are description of the error I am getting. I am not sure what is wrong though.
"Connections" in my flow are all ok (marked green).
"message": "The response is not in a JSON format.",
"innerError": "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01//EN\"\"http://www.w3.org/TR/html4/strict.dtd\">\r\n<HTML><HEAD><TITLE>Bad Request</TITLE>\r\n<META HTTP-EQUIV=\"Content-Type\" Content=\"text/html; charset=us-ascii\"></HEAD>\r\n<BODY><h2>Bad Request - Request Too Long</h2>\r\n<hr><p>HTTP Error 400. The size of the request headers is too long.</p>\r\n</BODY></HTML>\r\n"
What is the full path and file name? Is it very long or buried deep in multiple folders? If so, try creating the file in the root of your OneDrive and see if the flow runs without issues. If your file is in a folder path like this, the path length is probably what the error is complaining about:
/2026 Projects/Division A – North America/Regulatory Compliance/Internal Audits/For Review (DO NOT TOUCH)/Drafts (Old)/Historical Archive (Final)/v1.2/
Every special character in a folder or file name gets URL‑encoded, which increases the length of the path. Power Automate and OneDrive both have limits on how long a file path can be, and once you hit those limits, the trigger fails.
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