Make sure all parts on the board are in their sockets (especially memory)
Make sure boards (two board design) are plugged together
Make sure unit is completely seated in the backplane
Make sure front panel screws are in
Make sure IDE cable is correctly in place on P2 backplane if using IDE and 7452, 7455, 7459 or using an ACC-0562.
Make sure all front panel cables are secured.
Verify unit CMOS is configured properly or load the CMOS Default Settings.
If having CMOS problems such as resetting of the values previously entered after board was powered off... verify the battery voltage.
If SBC fails to output anything to your monitor after initial power, try clearing the CMOS (see SBC manual for instructions).
Make sure of system Airflow is equal or greater than the SBC recommended specification. Verify system +5V and +/-12V if having problems.
Check for bent pins in P1/P2 connectors or backplane, especially under a cable connector.