I cannot hear audio for some channels via Remote Monitor
If you have added a new channel to VRS while Remote Monitor is active then the new channel will not be monitored until you exit and re-run Remote Monitor. Otherwise have you checked the channels in Remote Monitor to signify you wish to listen to the audio. Lastly is there audio recording on the channel(s) in question.
If you are in doubt about whether VRS Recording System will do what you want we recommend you try the free download. Seeing the program in front of you often answers most questions