OMG, that was the problem. I had:
amixer Simple mixer control 'HDMI',0 Capabilities: pvolume pvolume-joined pswitch pswitch-joined Playback channels: Mono Limits: Playback -10239 - 400 Mono: Playback 120 [97%] [1.20dB] [off]set to off
So, after doing amixer sset HDMI unmute :
Simple mixer control 'HDMI',0 Capabilities: pvolume pvolume-joined pswitch pswitch-joined Playback channels: Mono Limits: Playback -10239 - 400 Mono: Playback 120 [97%] [1.20dB] [on]Thank you very much!