This error means that VirBELA is being blocked from sending traffic for voice over IP communication (VoIP). VirBELA is, at its core, a social program heavily reliant on internet connectivity. Core functions of VirBELA will not operate correctly if VirBELA is not allowed to access the internet.
If you are on a corporate or business network, speak with your IT department to allow VirBELA through your company's firewall. The information your IT department will need in order to allow VirBELA access will be present in the error in the voice server error. Usually it's a matter of opening UDP ports 5060 and 80 to allow information to be transmitted and received.
If you are on a home or personal network, making sure VirBELA has a clear path to our servers is a bit more complicated, but not an insurmountable feat. The three most likely culprits blocking the connection are: routers, firewalls, and anti-virus software (often inclusive of firewalls). There are far too many options for each category to discuss in any definitive capacity, but the general goal is to search your documentation for words like "blocking" or "firewall" to understand how your hardware or software may be blocking connections.