I'm trying to get Jira Server to fire a webhook to MS Teams whenever a version is marked released. I went through the setup and selected the Version: released event, and grabbed my webhook url from MS Teams. When I go to test it and release a version, nothing shows up in Teams and all I get in the Jira logs are a "Client error - 400 when posting to web hook" warning. I tried adding different events and just get more of the same. I am not specifying any JQL (though have tried it with some), exclude body is not turned on, and I have no linked transitions.
The other posts I've found of other people with a similar problem, it just seems to start working again. Any ideas what I can check next?