Disc drive is not reading discs.

This Xbox 360 slim was reading discs at one point but I had taken out the laser and put it in another model that needed it. Now I’ve ordered a new disc drive and put the laser in this model and it won’t read discs. When I put a disc in and close tray it says reading and then stops after literally 3 seconds ( I timed it ). I bought this disc drive with the new laser in it from a seller on eBay who didn’t say whether or not it’s working but they did say their Xbox had a RROD after I had messaged them.

Looking for help on what I can do.