We are doing a ZDU from 12.3.x to 21.0.x. In Step 3 of the ZDU all new processes are running, but the JCPs do not open the WS-Port, so the new jetty-AWI cannot connect to the JCPs.
Works as expected, this is normal behavior see resolution.
Release : 21.0.2
Component : Automation Engine
You can proceed to Step 4 of the ZDU: Once the PWP has switched to v21, the JCPs will provide the websockets necessary for Jetty-AWI to connect.