We need to understand how far the unit is reaching during the POST sequence. This means that we need to check the diagnostic LEDs on the board as well as any possible beep code that would provide us more information about this issue.
There is no jumper setting that would force the unit to go to the BIOS. However, based on the description you provided I have my doubts that the unit is reaching to a state that would load the BIOS screen after all.
Are you able to test the unit with different memory and/or power supply or processor?
Is this board known to be working fine? Was it used before?