AK3 Hdmi issue

[The Agony]

Hello, I have recently bought an AK3 mini desktop pc, I setted up windows (updates, driver) and installed office and firefox, the problem is with almost any software, if I put any software to full screen (in 4k or fhd) on the hdmi output, my 4k TV loose the signal (it says "no input"), the only solution is to presso win+D on the keyboard, so showing the desktop restores the signal.
As I bought the PC mainly to watch streaming contents it is a big problem.
As now I don't have another 4k hdmi cable, I ordered it to check, tomorrow I expect the delivery so I can try with another cable.
Meantime any suggestion is appreciate.

Thank you
Alessandro

[The Agony]

Problem solved changing the HDMI cable