After Fan Repair, Discs are No Longer Recognised

I followed the guide to replace the fan on here. I managed this, PS4 turns on, works fine, plays digital games. Then I tried to insert a game disc to play but every time I tried to load the game, it would say the disc wasn’t inserted. My optical drive did have a bracket on top which I didn’t remove at any point in the repair. Is it the wrong way round or could a loose cable be the culprit? Where you insert the disc did feel very high up but as a new PS4 owner I don’t know if this is significant. Any help would be greatly appreciated. Thank you very much! Let me know if you need any more detail!