I'm not sure I understand whether you tried the change in my last post. Did you update the cPanel module as I described here and try to save the server details, create a package using that module, and then generate a service successfully on that server?
I'm trying to determine whether everything works correctly with the cPanel module if Blesta no longer attempts to verify a connection, and thus no longer gives you this error when saving a new server:
If you did make that change, and the service still fails to be added, what data is available in the Module Log related to it?