www.makemkv.com

I am on a mac. 10.10.6
I have an internal drive and an external Blu-Ray drive. Make MKV finds only my internal drive even though I can play from the external.

Anyone?
Cheers!

The way it generally works is that MakeMKV asks the operating system, "Hey, what optical disks do you have that I can use?" If the operating system doesn't list a drive, MakeMKV won't look for it.

I'd suggest unplugging the external and plugging it back in, so that MacOS re-evaluates the drive. All operating systems lose track of things once in a while.