My fiancee has the Verizon "Wireless Home Phone" T2000 gadget (https://www.verizonwireless.com/home-office-solutions/wireless-home-phone-t2000/).
When I call her from my Verizon Wireless line (OnePlus 7 Pro with HDVoice/VoLTE) or when she calls me from that gadget, I can't hear anything. She can hear me, but all I get is dead silence. I have to hang up and call her back on her actual cell phone (also Verizon with HDVoice/VoLTE on Samsung J-something). On her cell phone, there's no problem.
When I call her from my other line (same OnePlus 7 Pro phone using a cheap AT&T mvno without HDVoice/VoLTE in the 2nd sim slot), there is also no problem.
Long story short, her Wireless Home Phone T2000 can not talk to my VZW OnePlus 7 Pro with HDVoice/VoLTE whether I call her or she calls me. All I get is dead silence. How do we fix this?