Hi Nathan,
SIP Softphone has to have a continuous connection to the microphone on the headset. If the audio path to the agent is disrupted for example by the VPN going to sleep or the agent disconnecting their headset, then the audio path no longer exists and an attempt to deliver the call will give you the message you are seeing.
If the softphone always gets this message then there is likely to be a problem with the network, such as the RTP traffic is being NATTed or the wrong network adapter being selected in the SIP Softphone Options.
If the problem is a temporary loss of audio path then reprovisioning will fix the symptom, but you might want to set the SIP Softphone to use persistent connections so the VPN doesn't time out so often.
Genesys recently included a patch to enable the softphone to autorecover from going to sleep, so you might need to ensure you are on the latest patch level if you feel that is applicable to your situation.
Cheers.