Check to make sure coin mech or dollar bill validator has power. 

1) Coin mech is powered from the game power supplies and is 12 volts. when a coin passes thru the mech it will send a 5 volt signal on the white wire to the game to credit. If there is power to the mech and no signal coming out replace the coin mech, If coin is constantly rejected by mech make sure there is a comparative coin in the mech to compare coins too.

2) The dollar bill validator is powered by 110 or 220 volt AC and gets it's power from the main power switch of the game and is on house current. If the bill acceptor takes cash but goes not start the game check the signal line for a start pulse.

3) If both the coin mech and bill acceptor are working properly and still no game play change out the U0 input chip and retest.