Error when opening the web interface

[AMG6900]

So I installed Plan on my minecraft server that is running paper on 1.21 and configured it. When i try to open the web interface I get this error.

{"error":"The required authorization heads were not present in the request."}

I'm using Plan 5.6 build 2883

Also I've got this error before when tried to use the squaremap plugin.
Can someone help?

[AuroraLS3]

It sounds like something other than Plan intercepted the request - there is no such message programmed in Plan. I'd ask your host :)

[AuroraLS3]

If you're using cloudflare that could be a reason, they only allow specific ports when proxying https://developers.cloudflare.com/fundamentals/reference/network-ports/