Before trying through your hosting provider, did you try through another cloudflare partner or through cloudflare directly? If you are unable to determine that or do not know the answer, the only option is to add the domain to your account here and change the nameservers with your domain registrar.
But I’ve tried through my hosting provider before and everything works. I recently created a new website and connected through my hosting provider.
I will try to explain briefly.
Everything that I use to connect cloudflare for this domain, I did it before, and after that domain (I mean other domains). The only difference with this domain is that when I changed the server (I changed my hosting plan), I removed this domain from the cloudflare.
The only difference, I want to say that I changed the server for other domains, only this time I did not remove domains from the cloudflare with this tool that you can see in the image. And everything works fine.
Now I am unable to reconnect this domain because I believe the tool has not completely removed this domain from the system. This is why I get the message: “domain is already registered.” Oh … and the message also says “with a different email address”, but it can’t be.
So I think the solution is “simple”. Could you please remove any information about this domain from your system so that I can connect as a new user?