This is an easy answer. You need to remarry the ps3 to that Blu-ray drive. What is the slim you are using, 120, 250, 160, 320 and so on. Also did you keep your old control board from the bad Blu ray? If you did this would make remarrying them alot easier. If not the only way that I have seen yet is to be on 3.55 and lower.
See you can't just go out and get a new drive and stick it in. They are paired to one another the control board on the Blu-ray and the motherboard. That is why I asked what is the ps3.
If you have the control board you might be able to get away with changing the the control boards And keeping your old one in the new drive. I know this is what is wrong because they will play DVDs and music but no games. Thanks