Help please! Screen all gray!!!

An olderSamsung tablet. It won’t power off. Screen is completely grey. Just went grey while playing my tournament last night. Battery was about 80%
Do you have any Ultra power saving modes on?
 
Press and hold Power and Vol Down for about 30 seconds to force a shutdown. Then wait a few seconds, and then press and hold Power again for about 30 seconds. If nothing happens, then the motherboard may have failed.