Next.js Server Action - Error 405

HTTP 405 is “method not allowed”, which means that the HTTP request method (like GET, POST, HEAD, PUT) isn’t accepted by the API end-point.

It may be related to this Bug: CF Captcha randomly changes file upload POST to GET in which a bug in Cloudflare causes the browser to randomly change a POST to a GET, which can easily result in a 405. Cloudflare did change it yesterday, but also introduced a related problem when sending POST requests.