Cannot join UCS domain: "An unknown error with status code 502 occurred while connecting to the server, please try again later"

Hello,

I have an UCS master running, and now trying to join a UCS slave. I did a fresh install from iso, but get stuck at the step to join the UCS master. I gave ucs master IP address as the nameserver, chose the system role as “Domain controller slave”, the hostname of ucs master was correctly detected, entered user = Administrator, pass = pass of Administrator on ucs master.

I get the error “The connection to the UCS DC Master was refused. Please recheck the password”, which could be fixed by ensuring that ssh on master is running on standard port 22 and password authentication is allowed. After that the installer seems to do something when I clicked NEXT for a few mins and then gave the error

“An unknown error with status code 502 occurred while connecting to the server, please try again later”

I also tried to disable the firewall on ucs master (it’s running on a public VPS), same error.

Does someone have an idea what can I try to debug the problem?

Regards,
Tony