new nw65sp4a server added to nw51sp8 network. NDS 8.73.4

nw51sp8 server inplace upgraded to nw65 sp4a about one month later.

NRM is abled to connect at

Old nw51sp8(now nw65sp4a) server can only connect via port 8008. It
cannot connect via 8009. We did not notice any problems with pkidiag or
sdidiag during the inplace upgrade. Pkidiag currently does not return
any errors.

It would appear that something with the certificates is not working.
How do you proceed to diagnose this and resolve the ssl problem.