You don't have any Layer3/Layer4 issues on those flows, do you? Can they ping each other? No software firewalls are running on the PCs, are they?
If you get a packet capture on the endpoints, do you see RTP being received? Can you get a capture off CME's switchport that faces the PCs with the soft clients? Do you see RTP packets in/out there?
DK is correct, the CME BU does not support third party SIP client registration to CME. Other than with community support, you're on your own if you run into defects/bugs on these devices, or if they don't work.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.