Primary SpectroSERVER was successfully upgraded to 10.4.2, according to "Upgrade Best Practices Fault-Tolerant Deployments" Archmgr on Primary SS were to be started first, prior to starting Primary SS.
However, when I tried to start ArchMgr from Spectrum Control Panel, it did not work. We got the SPC-OCP-10069: The Archive Manager has been shut down because it could not find a SpectroSERVER to connect to.
The Secondary Archive Manager was connected to the Primary SS, preventing any new connections.
The Location Server (locserv.exe) process on the Secondary server was down. The Secondary Archive Manager was not able to connect to Secondary SS, and instead found location sever on Primary SS. When starting Primary Archive Manager, it had no open SpectroSERVER to connect to.
Release : 10.4
Component : Spectrum Core / SpectroSERVER
Restart processd on Secondary server, which in turn restarts locserv.exe process. Now, Secondary Archive Manager can connect to Secondary SS, and Primary Archive Manager can connect to Primary SS.