The v12.3 Agent was successfully installed and started, next to older v10 Agents.
The Agent log shows that it connects to server, but the agent then terminates the connection with following error message in the Agent log file:
U02000105 Error when calling the function 'gss_acquire_cred' (Ret='458752', minor='1004').
An old v10 agent can still successfully connect to the new v12.3 Automation Engine.
Release : 12.3