Wifi Connection 5GHZ Rasp4B

Hi guys,

having a little trouble with wifi connection on raspberry pi 4B.
First of all, I cannot find my 5GHZ wifi in the list of scanned wifi SSID even though when I was on librelec I can connect to it without problems.
Moreover, the connection is really unstable, I have to run the install command multiple times because sometimes it cannot connect to server, but I have never had stability problems with my connection.
The language and timezone are set up correctly.

Anyone can help me?
Last info: on the rasp4 I had liberelec before, but to install dietpi I used a new microsd and just changed the sd cards, don’t if this can cause problems

Thank you!