Input devices not detected

I am trying to fix a fault on my cousin’s old Medion computer. The problem is that the computer boots OK but the input devices (keyboard and mouse) are not detected. The devices use PS2 connections. With persistence I have had it boot twice and detect the keyboard & mouse but after a couple of minutes they stop working again. Any suggestions would be appreciated. The computer has been moved to a new house recently it could be something disturbed in transit.

 

Make sure the keyb/mouse are inserted correctly. Purple = keyboard in the lower connector; Green = mouse in the upper. Disconnect power cord before unplugging PS/2. Also, try another pair.