Improperly ejected my external HD now Mac doesn't see HD's

[dgerch]

Forgive me if I sound totally ignorant.

I have a Mid 2012 MBP running Sierra with two hard drives, One SSD that's my primary drive and I swapped out my optical drive with another HD.

Today, I improperly ejected an external hard drive as it was copying some data and since then my other, non primary internal HD (not the SSD) is unreachable. There is no icon on my desktop that says "Mac HD" and I'm unable to find it in my finder. In addition to that, when I plug in my external hard drive, it is not read by the computer.

I've tried restarting, restarting while pressing option and attempting to load from the other Drive (It sees it at that pre-loaded moment) and a variety of other things.

As you can see, my understanding of computing is very remedial. How do I fix this?

 

[Gav2k]

Plug it in open disk utility, select the drive then repair it using the options on the right.

 

[dgerch]

Plug it in open disk utility, select the drive then repair it using the options on the right.

You know, I've actually tried that but disk utility just says "Loading Disks" forever. It gets stuck.

 

[Fishrrman]

If you haven't done this yet...
Shut the computer down -- ALL THE WAY OFF.
Wait 30 seconds, then reboot.

When you get to the finder, open disk utility.
Can you see the 2nd internal drive?

 

[dgerch]

If you haven't done this yet...
Shut the computer down -- ALL THE WAY OFF.
Wait 30 seconds, then reboot.

When you get to the finder, open disk utility.
Can you see the 2nd internal drive?

I have tried that. When I run disk utility it either will load disc forever or show the other internal drive (Macintosh HD) but it will be grayed out, as if it's unreachable:

When I press "mount" nothing happens and when I attempt first aid, it shows this:

Again, this all happened when I improperly ejected an external hard drive while it was copying something. The computer wasn't dropped or damaged in any way. Ever since I improperly ejected this external drive neither my secondary internal drive or the external are being recognized. Thanks again, by the way for taking time out to help.

 

[CTHarrryH]

I've also found once that it took the external HD about 30 minutes or more to show up. I was in the midst of doing other things and was going to get back to the problem and when I checked the drive showed up. Not sure of exactly what it was doing.

 

[Fishrrman]

If nothing else works, you might try this (yes, I realize it's "a job"):

1. Take the secondary drive OUT of the MacBook, tack the rear plate on with a few screws.
2. Put the drive into a USB3/SATA docking station, or a USB3 enclosure, or use a USB3/SATA "adapter dongle"
3. Don't connect the drive yet
4. Boot the MacBook.
5. When you get to the Finder, connect the drive and.... WAIT a while. Give it 30-45 minutes if nothing else happens.

Do this, and report back with your results.
You -might- be able to access the drive that way.

At the worst, IF you can get the drive "accessible" using Disk Utility, you could re-initialize it.