For Volicon 7.2 there are 2 player clients, the Observer Web UI and Observer Pro client. If video is not playing in Observer Pro, but the same channels can be seen playing in Observer Web UI, it is necessary to stop then start the Observer Policy Service on the Probe that hosts the affected channels.
If restarting the Service does not fix the issue, please check that TCP/UDP ports 4504, 5502, and 943 are all open and listening the Firewall of the Probe host. It will also be necessary to make sure the Central Server and Client PC's can access these ports as well. Following is a link to Volicon documentation on the necessary ports to be open for version 7.2:
