Router doesn't accept phone numbers, another one does?

Hello dear community, I switched providers for my grandpa from Telekom (5 Mbps) to PYUR (50 Mbps, which markets the VDSL line the city built). I've been a PYUR customer for years myself, and I live in the same town as my grandpa. While everything went smoothly for me back then, here I'm having nothing…

Fritzbox sporadic SIP error messages – serious cause or normal?

Note: I have revised the question description: A new detail about FRITZ!OS at the end of the question description! Sporadically, about every 10 days (sometimes it can be just 5 days or up to 1 month), this message appears in the telephony event log on my Fritzbox: Registration of the internet number xxx was unsuccessful….

Yealink?

I'm switching from Snom to Yealink (T48G) at my company. Since these phones have touchscreens, new possibilities open up. Is there a way to display information on the screen? I'd like to implement time tracking on the phones, among other things. If necessary, I could think of updating the background graphics with the information needed,…