My family's Internet randomly stopped working 2 days ago (the Info LED turned red on both the master and the slave - master is 7590, slave a 7490).

Today I was at their house. I rebooted both fritzboxes. Now the info light was yellow as usual but still only getting Connected but no Internet access.

I connected by ethernet to the laptop, and all works great so issue seems limited to WiFi. I deactivated the WiFi function and re-enabled in the Fritzbox admin page and my phone started working on WiFi. But as soon as I stepped out of the room (just over a metre away), and it went back to Connected, but no Internet access.

I tried with my family's devices, iPhone 13, MBP, Windows laptop, S22 and Huawei.
Every single device exhibited the same issue. Works in the one room, but not if you step out. I know for a fact it works in the hallway.

I had brought my own FB 7490 from my house to test and it works fine outside the room (even though I hadn't reconfigured the slave).

Fast forward, my brother calls 2D who proceeds to factory reset his modem (not that it seemed my brother was aware that was what he did). Was told, your modem wasn't configured correctly. Don't change the SSID else it will stop working again. Only change the password. lol? How come it worked for a solid year with no issues?

A bit of a nuisance as I hadn't taken my slave out of Mesh mode so now it's stuck in a state as I can't open the admin page with the usual admin IP, but also my VOIP config is gone.

However more curious how the WiFi was able to end up like that? As after the factory reset, it does appear to be working outside of the room.