video resolution on RP4

  • I've a RP4 4G with Libreelec 9.2.3.

    when the system starts, the maximum video resolution is 1024*768 and I can't change this resolution for see a 4k resolution on TV.

    TV is a samsung Q60 and until recently the raspberry sent the signal in 4k resolution. I don't know what I could have touched for getting everything wrong.

    Is it possible to restore a video resolution that allows me to see the signal for the RP4 in 4k?

    I tried to insert the lines in config.txt

    hdmi_mode = 0

    hdmi_enable_4kp60 = 1, but nothing happens and even restarting a new libreelec on microSD