The items below are some of the things that often contribute to VoIP problems. Thus, when VoIP’s not working, be sure to check these:
Cable connections: All cables must be plugged properly and securely. Inspect them every now and then to ensure that there are no damaged cables.
Hardware equipment: Your VoIP phones must be up to date and registered with your VoIP provider.
Internet connection: The internet bandwidth must support the volume of calls in your call center. Upgrade your plan if necessary.