405 POST on Pages website using React

Hi, I have been trying to integrate a slack feedback feature on my website using React and have been able to successfully make it work using a POST request on form submit.

This only works on either localhost or on a web provider that is not Cloudflare. Whenever I try to submit (or POST) in the pages deployment it gives me an extremely generic 405 error.

Is there something obvious I might be missing? Do I need to use Workers for this? Is there some rule I must activate? I am quite lost. Have been at this for about 5 days reading forums, exploring all options and nothing I did was able to fix it.

If someone could clarify what in Cloudflare is blocking this, It would be greatly appreciated!

Thanks in advance.