I have a RB 951-2n and the wifi just soped working for all my devices.

I have 4 devices:
1.) smasung notebook with an intel wifi card
2.) nexus5 phone
3.) samsung galaxy s3 mini phone
4.) a lenovo tablet

all devices were working ok until yesterday. I have made no updates to the router or to the devices. Also a wired connection trough the router is working ok, so I assume that there is not a problem with the ISP.

At the time I started to have problem I had RouterOS 5.20, then I upgraded to 6.33.3 but the same problem persists.

Two f the devices does not even connect anymore (the laptop, and the samsung phone), the other two connects sometimes but drops the connection soon, and even if they manage to retain the connection, the data transfer is not working (no internet)

How can I even start to debug this issue? It is very strange because for 4 months it was working great.

I have restarted the router several times to the default factory settings, and also tried to leave the WIFI open (no security) and try to connect but the same problem persisted.

Hello,

did you tried to change the wifi channel ?

on I have not, maybe I should find out first which channel is best

Reboot wifi and try?