can't access anything except google sites when connected trough router
So i have a Range extender in the top floor connected to my Archer C6 downstairs, has been working fine for a few years now. All off the sudden i can no longer access anything except google, first i thought it was my computer becuase every other device seemed to work fine. I tried the basic fix of switching DNS, resetting TCP/IP etc. i even tried resetting my adapters. After everything failed I figured it had to be something with the extender. I checked and sure enough my other devices were not connected to the extender.
I tried resetting the extender but nothing changed still no connection, i reset my router, still no connection. I reset the modem, then the router, then the extender... still only google and youtube i can access. Now i changed the extender to be directly connected to my modem and all of the sudden my internet is back. What can cause this issue and how can i resolve it, the connection with the router was better and i am missing some performance.