Superdrive HDD replacement not working

Hi

I've just worked through the guide to change my superdrive for an additional HDD. At the same time I also swapped the HDD for an SSD to boost speed.

Which ever drive sits in the original HDD bay seems to work perfectly (currently sending this via the SSD). However, the drive sitting in the superdrive replacement bay doesn't seem to come up on the desktop, or even be findable as far as I can tell.

I double checked that all of the connectors are snapped in (and they are as far as I can tell). Is there something I can do to find the other drive, or would it be possible that I need a new optical drive ribbon cable (or could to connector on the logic board possibly be an issue, in which case yikes!).

I don't know if the superdrive was working previously - I assume so as I bought the machine 2nd hand but in working order, specifically to swap it out.

Any help gratefully received.