Asustor AS5202T (Nimbustor) not showing anything to TV via HDMI

Hi,
I have recently purchased an Asustor AS5202T (Nimbustor), including a Remote Control AS-RC10, connected the NAS via HDMI cable to a 4K TV but, changed HDMI input to the correct one but still I only get a black screen.
What am I missing ? Do I need to install/launch some particular service/server on the NAS ?
P.S. I used to do the exact same procedure with an older AS6404 and it worked just fine, without installing anything particular.
Many thank in advance.
I have recently purchased an Asustor AS5202T (Nimbustor), including a Remote Control AS-RC10, connected the NAS via HDMI cable to a 4K TV but, changed HDMI input to the correct one but still I only get a black screen.
What am I missing ? Do I need to install/launch some particular service/server on the NAS ?
P.S. I used to do the exact same procedure with an older AS6404 and it worked just fine, without installing anything particular.
Many thank in advance.