PS3 super slim not reading discs at all

Hi, I have recently replaced the disc drive (complete with new laser as that was what I suspected the problem was), I have also completely restored the system and done all the options on the PS3 service menu. I have done “hard” and “soft” resets multiple times, have tried any number of types of discs, and nothing works. I made sure the disc drive would spin the disc before reassembly but as soon as I put the hard drive back in it’s stopped working. Everything was working perfectly before I installed the 4.85 update… does anyone know how to maybe install an earlier update like 4.84 (have checked sony’s Website & there’s nada)? Or maybe if I just need to manually re-install the latest update?? (If it’ll even let me do that idk— I have no error messages that would suggest the update was interrupted/corrupted). Or if the problem is with my hard drive?? I really don’t wanna have to replace my whole console.