EX6100 extender not connecting to router

So it’s been a few years since I’ve used this extender, and the model is quite old. It worked find before but now it’s having trouble connecting to the actual router itself. The router and extender are both in the same room I literally put the beside each other at a point, still says “can’t find the router” I’ve tried literally almost everything, restarting, power cycling, forgetting and reconnecting, rebooting, restarted both router and extender multiple times. I’m at my wits end now and finally coming here for help, else the customer service wants me to cough up money just for a 1 day service.