Cloudflare Tunnel Connection I can't get a connection. Error 522

Good afternoon.
I’ve been trying for several months to set up a tunnel connection with CloudflareZeroTrust so that I can access my home assistant from the internet (outside the local network). I have done all the necessary steps for the correct configuration using a domain that I already had with IONOS (the tunnel appears to me as HEALTHY) and everything seems to be correct (I have the external servers configured in my domain provider, IONOS, etc) but when I try to access with my domain address + port it indicates error 522.
I was recommended by Cloudflare to contact IONOS, but they tell me that their entire setup is fine (I transcribe their answer for you):
We inform you that the error you report does not correspond to the connection of the domain, but to the response offered by Cloudflare from its server. As you can see in the propagation of the domain, the connection is complete and correct, the fault comes in the response obtained.
It should be checked by the other provider. and that the problem is Cloudflare’s, and by each other, I’m unable to fix the problem.
Can you please help me fix the problem?