i have the same issue with my monitor.
At home connecting the board to my monitor(asus) brings just the black screen. monitor wakes up periodically and then goes to sleep.
At work i use dell monitor 2412M and it just works.
So at home i have to use my TV, i’ve tested with an old toshiba and with new panasonic, on both it just works.
make sure that the hdmi cable is connected before you plug the power.