It sounds like the IP Communicator is using the wrong codec type to communicate with the gateway to the PSTN.
Can you make calls from IP Communicator to internal phones ok? If yes which codec are you using? (probably G711). If not check whether you have IP Communicator configured to use low bandwidth codecs.
Preferences > Audio > Optimize for low bandwidth
If yes turn this off. If you still cannot call an internal phone then review the Partition, CSS and Device Pool settings of the IP Communicator softphone and set these to be the same as those of a phone on the internal network and then try again.
You should hopefully be able to call an internal phone now but will probably be using G711 (80 kbps per call). If you have the bandwidth to support this over the VPN great. If not then you will need to configure regions to allow you to use G729.
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.