led display losing some dots is possible.

but if whole display gone and hdmi no output, not a good sign.

try checking the connections again.

last resort, consider flashing the unit and reinstall firmware 107 with the restore pin - but this will erase everything inside - hope u hv backup.

if no good, then likely hardware failure.

which will the first case i know of.

i have q5ii >2 yrs, still very good.

at the side of the device where the usb slots are, there is a pin hole labeled "restore".

insert a usb drive with the firmware at root level.

when ready, push a pin or toothpick into that restore and hold it while u turn device on.

this method to erases everything in it, install fresh firmware.

after that, u need to to reinstall the apps from a backup if u hv one.