how to make macbook discoverable

Yes, we do have the same one. It is much more reliable on our newer devices, but the 2012 will only react when it's in the mood, LOL. In order to be able to use some older apps, I am keeping that one on Sierra (was going to do High Sierra, but it rendered it completely non-responsive and it took 3 days to revive it (it would not respond to anything, would not boot and wouldn't recognize my external backups), so I am not upgrading that because of that as well. I've pretty much given up on it.

Odd. As I recall, we have the same model (13-inch 2012 non-Retina MBP upgraded with SSD).

I have the same model MBP and on mine, it is very haphazard: it will work if/when it wants to and most of the time, it does not. It is unreliable and mostly we have to resort to email or drag it to a USB stick or similar.

what year is it and what model year is the other device?

here are the requirements for airdrop

https://support.apple.com/en-us/HT203106

That Mac is compatible. I have the same model and AirDrop all the time to/from my childrens' iPhones. I use the "Go" menu option shown in the article babowa linked.