wifi calling doesn't work

I have 1GB wifi that's connected to a Linksys Velop mesh network. I'm able to download in excess of 200mbps wirelessly using my iPhone 6. Despite this, I'm rarely able to connect to wifi-calling, which is essential due to the poor cellular reception at my home. I've tried all the standard troubleshooting fixes: restarting my phone, turning wifi-calling on and off and resetting my network connections, but nothing works. Many months ago it worked reliably so I have no idea why it isn't working now. I have Verizon cellular service, which supports wifi-calling. Suggestions?