Here's the fix from Reddit:
"Called verizon tech services to discuss this further, a technician named Vince was super helpful and was able to help me to a solution. Below are the two things we did:
Reset network settings (Settings > General > Reset > Reset Network Settings).
On Verizon's side we found that my account was provisioned for HD Voice, Advanced Calling (two different provisions for the same feature), and WiFi Calling. We removed all three and turned on HD Voice and WiFi Calling. -- the technician then said he sent a command to sync my phone with the network."
We've all tried the network settings reset but not the others which are server based. It's worth a shot.