Update: I updated the firmware and now everything is working again! It seems there is some juice still left in the oldie.

@terziyski Yes, I've already tried that, with the RE less than a meter from the router. No dice. I guess its time is up. 2.4GHz still works, but that's slow.

My TP-Link RE305 stopped finding my router's 5GHz network, after working for years without any issues. I've reset it several times, I've renamed the SSID of the 5GHz network, the current channel is...