As read from the error, the cause is that DE HAC peer server was not reachable via RMI (Remote Method Invocation) call.
In order to poll each other, DE HAC servers use the RMI, and so their requests should be allowed to move through the networking media; check if possible devices like firewalls, gateways, routers do not block RMI.
NB. It is also a good practice to check if:
- The peer server is up and running
- The system's clocks on DE servers hosts are synchronized. Check the tracelog files of the Primary server for the warning message like this:
Handshake ... has a significant time/clock difference ... Please synchronize the clocks of the two servers.