AMP connector resolves private cloud server IP from FQDN of local configuration file. Probably that client can't resolve internal FQDN in out side of customer network. Also customer need to check firewall ACL for AMP connector's communication port from out side. I think this doesn't come from connector upgrading. All connector design are same using FQDN.
-Easy workaround is using VPN.
-Hard way is to open internal FQDN to public.
-One more unrecommended way is write host IP in hosts file of computer. However this is completely unsupported way and test purpose only. If you choose this, contact TAC first.
I hope this is help.