CD/DVD Drive Not Reading Discs

Hi everyone, I've been experiencing a problem with my MacBook Pro (Mid 2012) lately regarding the CD/DVD drive and I'm not sure what to do about it. I've tried looking through various other threads for a solution but nothing so far has worked.

It started out just occasionally not reading a disc every so often but at that point simply ejecting the disc and trying again used to work. Unfortunately one day it just completely packed in all together and now refuses to read discs at all.Sometimes I’ll get a warning message saying that the disc cannot be read, other times it’ll say I’ve inserted a blank disc (it's not) and other times it will just spin the disc round for a bit and then eject it with no explanation. It’s definitely not the disc as I’ve tried a mixture of CDs and DVDs and none have worked.

I’ve tried resetting the SMC and the NVRAM but this made no difference. I also tried First Aid in Disk Utility but that came back saying that everything was fine.

I then tried inserting a credit card with a cloth wrapped round it as suggested in other threads and when that didn’t work I put in an actual lens cleaning disc which also didn’t solve it.

At this point I was resigned to the fact that the hardware itself had probably failed and I would have to get it replaced, so I borrowed an external disc drive for temporary use. However, upon trying that the MacBook still won’t read discs even from the external drive!

As a last ditch effort I updated to Sierra this morning in the hope that might sort the problem out but sadly no luck.

I’m guessing it has to be a software problem still - otherwise the external disc drive would have worked right? But that aside I have no idea what to do going forward. Can anyone out there suggest anything I might try to get it working again?

Thanks in advance.