I wouldnt say its the IC yet.
If you had to put shrink tube on the leds, you might have a light refection/interference problem.
This will make you think you think it doesnt work.
Did you make a black paper shroud?
Optos are really frustrating.
Barring bad wires/contacts/traces etc. It should work.
Having a known good spare 10 opto board really helps.
I simply bought a new board.
They dont work right if:
1) They are always active due to reflection or light interference.
2) The beam cant be broken because it already is or misaligned.
So, either the beam cant be broken, or it already is.
Pulling the boards off the carrier and rubbing the transmitters and recievers onto each other during test can be enlightening.
Generally you can prove that each one does indeed work witj a little experimentation.
The rest is all about assembly tweaking.
Sometimes rebooting the game while testing helps to reset the game computer.