You may come across a problem installing a secondary node for cucm such as the subscriber node or CUPS. You check and try&try again. You probably don’t see any mistake but couldn’t pass this step.
Solution: If every credential is correct, I mean publisher cucm hostname, ip address, security password, dns settings, etc. , you added the new nodes to the publisher and then the problem is mostly originated from not being restarted publisher at least one time after you installed. One time restart of CUCM Publisher will solve the problem.