Recently I noticed that my iPhone was no longer connecting to VZW Wi-Fi while at work. I did a little digging and found I needed to add the following IP addresses to our outbound firewall rule for allowing Verizon Wi-Fi calling.
As soon as I added these, BAM, my phone started connecting to VZW Wi-Fi.
These two already existed:
As a side note, some time ago, we added the following IP addresses to allow T-Mobile Wi-Fi calling as well.