USB SuperDrive No Longer Recognized

first, to eject the disc, you can completely shut down the mac. then turn the mac back on and immediately press and hold the mouse button while the mac is powering up. this should eject the disc.

as far as getting the mac to recognize the superdrive again, there are a few steps you can try. the first thing i would try is to shut the mac down, disconnect the superdrive, power on the mac, and wait until it is booted before reconnecting the superdrive. if that doesn't do it, i would then try and reset the NVRAM / PRAM and also reset the SMC. you can learn how by reading the following links:

How to reset the SMC of your Mac - Apple Support

Reset NVRAM or PRAM on your Mac - Apple Support

you're welcome.

but since the PRAM and SMC resets were unsuccessful, and your mac has otherwise been unable to recognize the drive, i do have two more suggestions.

first, you can try and start your mac in safe mode to see if that solves the issue. if the drive then functions, restart your mac normally and see if the drive still works. sometimes a safe boot followed by a regular boot will solve issues. please see this apple support document: How to use safe mode on your Mac - Apple Support

and if the issue is still unresolved, you can set up a new user account and test if the drive then works on that account. this will tell us if the issue is related to your main account, or if it is system wide. please see this apple support document: Set up users, guests, and groups on Mac

and if none of that works, then unfortunately i feel that the superdrive has had some sort of mechanical failure. but before rushing out to buy another one, do you have a friend or family member with a mac that you can use to test the drive?

sorry, had to correct the link re setting up an account.