I’ve reset my Mac mini 2012 and now the drives aren’t recognised.

I reset the Mac mini as per instructions on this forum and all was well until I got to the reinstallation part. Now it doesn’t recognise any of the 2 drives that were both working before the reset.

1. SSD
2. Apple HDD drive

There is no disk to select to reinstall the os. When I’m in disk utility one drive is there (Apple HDD) but it’s called “internal drive” and after running verify disk and repair disk no errors were shown.

There are 2 options available against that drive

1. First aid
2. Partition

Every option in partition is greyed out and can’t be selected. Only other drive showing is disk 2 - Mac OS X base system.

any ideas on mounting the drives again so I can reinstall the os mountain lion back onto the ssd as it was before?

Is there any advice on what to do as apart from getting those 4 options, I can’t do anything else with it.

I’m confident that the drives are both ok as it’s way too much of a coincidence that both drives stop working after the reset.

Thanks