I had one iPhone at home that suddently didnt work on WiFi anymore, while there was nothing special about it. It turned out to be one networking or FaceTime setting somewhere, but I don’t know which. Here I document which switches I toggled.

Symtpoms ¶

• One iPhone/AppleID (‘iPhone H’) on iOS14 does not work with FaceTime over WiFi
• Other iPhone/iPad on other AppleID but iOS15 is unaffected
• No specific firewall rules for iPhone H
• iPhone H FaceTime works over 4G cellular
• iPhone H FaceTime works over 4G cellular + VPN to home network
• iPhone H FaceTime works over WiFi + VPN to same home etwork (🤯🤯🤯)

Solutions ¶

Basically, fiddle with settings until it works. The parameter space of settings is not divergence free (wikipedia.org), it seems it matters that you toggle settings on and off again.

1. In FaceTime settings: Make sure the blue tick is next to your Apple ID (you can verify because directly under the list of options, you’ll see “Apple ID: [your Apple ID in blue font]”)
2. In FaceTime ettings, where it says “Apple ID: [your Apple ID in blue font]”, tap on the blue font and a ‘FaceTime Account’ dialogue box will appear. Click on ‘Change Location’. Ensure it’s set to the country you’re mostly calling from. Also try to set it to a neighbouring country, and possibly back again.
3. In FaceTime settings: disable FaceTime and enable it again
4. In VPN settings: Connect to VPN if you’re using one, then make a call. Then disconnect VPN and call again

Sources ¶

SOLVED: FaceTime not working on WiFi but fine on cellular (reddit.com) FaceTime always drops WiFi and forces calls over mobile data - possible fix (reddit.com) How to fix Facetime connection issues on your iPhone after iOS 13 update (ikream.com)