We've recently switched to 2d broadband + landline, but the landline only accepts incoming and outgoing calls for like 20-30 mins after a fritzbox reboot, then it will only do outgoing calls (normal beeeeep when you pick up the landline). Give fritz another reboot and incoming calls works for a few mins again, then stops, etc.

So any calls we get while the fritzbox is denying incoming calls goings into 2d's built in voicemail system (not on the fritzbox), which I've setup to email me. At least that works.

I tried to email 2d about it, they took a week to reply asking to verify ID, done that, then a week later got an email saying they tried to call us but couldn't get through. They didn't call my cell, I have no missed calls, so they must have called the landline. Which is why I'm contacting them. The best they could offer was to reset the router remotely, which I've done, it doesn't help.

So I'm hoping I get more luck here.

My setup: I've setup our UDM to connect to 2d for internet, then plugged in there FRITZ!Box 7530 they sent us into the UDM.

All my settings in 2d's online portal are per default, as are the ones in the Fritz!Box (excluding what's needed to tell it to use existing internet).

FritzBox settings changed:

Internet > Account Information > Internet Connection

"Internet Service Provider": other internet service provider (setting to 2degrees removes the below 2 options)

"Connect via": Connection to an external modem or router

"Operating Mode": Share existing internet connection in the network (Mesh Wi-Fi / IP client mode)

I think I've left everything else per default.

The fritzbox reports everything is golden on for the phone line.

The "Diagnostics > Function" reports everything is good too.

And nothing to report on the "System > Event Log"

No incoming calls show in the "Telephony > Calls" - Call List, after those 20-30mins pass after a reboot.

Anyone had similar issues like this and know of a fix?