@Mattias Clouse Thanks for reaching here!
It seems like there is an issue with your deployment to Azure Static Web Apps.
A 400 error usually indicates that the server was unable to process the request due to invalid syntax. This could be caused by a number of things, such as incorrect configuration settings or missing dependencies.
To troubleshoot this issue, I would recommend checking the following:
Make sure that your Azure Static Web App is properly configured to use the correct build settings and environment variables
Suggest you refer this article on step-by-step guides to troubleshooting deployment and other issues for your static web app.
Please let us know if issue remains, Happy to assist you further.