@Vinser I solved, you need to put the 5Ghz channel on the 36 on the router. But I wanted to know why the router communicates with the extender has 2.4 Ghz? Thanks.

Hi, the led of the 5Ghz connection of my Extender tp-link RE450 (EU) has turned off for a few days s / n 218C833001229 ver.2.1 I state that my TIM router regularly transmits the 5Ghz signal. I seem...