My pc is turning off automatically every 30 minutes even at bios.

hi I was using this pc HP Compaq 8100 Elite Small Form Factor PC for 2 years now and for the last 10 days I removed the rams for some reason and it started to switch off automatically every 30 minutes exactly no more no less, it also displays on the blue screen this message, " Management Platform is in Manufacturing Mode", I have tried power and sleep options, cleaned the pc, increased thermal (fun)  and reduced it no change, also no bios update is available since 2012 and it is not even installing, resetting the bios and CMOS didn’t work, tried bios utility. no sign of hope it would help if you guys could tell me any solution. my motherboard is Hewlett-Packard 786h1.