I have one that wouldn't show anything except the settings gear icon - if you can get that to open, give it a factory data reset. I did that and it all came back perfectly
The KM2 has a mode where if a file is put on a flash drive, the device will do a factory reset.
I don't know if it works on the KM2 PLUS also, but both the KM2 and the KM2 PLUS are manufactured by Skyworth, so maybe there is a chance it will work on the KM2 PLUS too.
https://forum.xda-developers.com/t/skyworth-hp4024-hp40a.4425361/post-87120519
Do you have an SD card inserted?
If you do power off the box, remove card and reboot without the card inserted.