As a follow-up...I uninstalled TM Server 6.0 and reinstalled TM 4.4.5 with the same results. Based on a comment from another forum, I found that Windows Management and Monitoring Srvice was not installed, so I installed it. I can now see the status of my Firewall, but still cannot access it to change it. (I'm thinking maybe the Firewall is affecting the service.)
Further information, this is true of two separate DSM-320 media players. Neither one can see the TM Server. Again, the TM Server lists the units as requesting service, complete with correct IP addresses.
I do not have the password turned on in TM Server.