networks: the Wifi extender stopped working and does not work again for more than a few minutes

So I have this wifi extender that has been running for a month and now I suddenly decided not to work anymore.

It does not grant me access to the Internet, I restarted it from the factory and I proceeded like a month ago, when everything was fine. I enter my main Wi-Fi on the extensor's web interface, I create the extension network and then it works for a minute or even before I stop connecting to the Internet and, what is more strange, even when I connect to it, I no longer I can access your web-based interface unless you reset the factory settings ** Any clues? I'm going crazy for this …