Check your +12 v and make sure its at 12 v. Check J101 on Driver board is well connected and header pins are soldered in good. A.S.A.P. Always start at power.

Do you have a manual ? Look at page 2-11 it shows the Driver board. in upper left to teh left of Fuse 115 is Test Point 3. Which is regulated 12 volts. I would check that first and just to the upper left of that is TP1 which is unregulated 12v. The opto's use the regulated 12volts Place the black lead on ground and the red lead on the test point. If that is getting good 12v, i would then check the 24opto board you can see schematics of that on 3-24 of the manual. J1-1 is (Switch 82, Ball On Magnet) to photo tranistor board emitter) and J1-3 is the +12 going to the Collector for that opto. You can test the 12 volts there making sure that opto board is working and properly sending out the +12v to the opto's. (also make sure all connectors and wires are secure here). If you have good 12v there you can test the actual opto's located in the ball gates.

could also be opto's not properly aligned? Make sure both opto's are screwed in tight and not loose.