The Verizon VVM (visual voicemail) app does not use standard internet browsing ports like 80, 8080, or 443 for accessing voicemails. This can be an issue if you are connected to WiFi, or a VPN that filters traffic. I was not able to find this information doing a basic Google search so hopefully this will help others having issues with this app.
Verizon voicemail app uses the following domains:
vi1iv.myvzw.com Port: 143
vi2lv.imsvm.com