I've got a range extender (TL-WA854RE) and it's been working just fine for quite some months. But lately, and I have not changed the router, my devices suddenly stop listing its SSID in the network config while the lights in the extender are right. Sometimes devices get signal, sometimes they don't and I've purposely tried with several phones and pcs. Sometimes it even shows the SSID but they never get to connect to it and when they do, after a short period of time they disconnect and lose signal again. Any idea of what's going on?

Already tried to reset it, and the router too. Again, lights on the extensor say everything's all right.