Good signs. Appears to be SSD.
Sounds encryption based. Did someone add a password? Was a password on it?
Do you get the same symptom when connected to any other devices? Not sure how I'd handle the scan you're stuck in now....
Discussion
I plugged it into a friends laptop last this week to grab a bunch of files.
🙄
If you connected it to another computer, there's also the possibility of a virus, ransomware, etc? Maybe? ....
However, I've had the experience of using an external drive on different machines and it messing up the permissions on the drive. If it will mount on a linux machine running a live-dvd environment, you might see if it's only a permissions issue. If it is and the files are all only data files (videos, text, pictures, docs, etc) and not software or a system, you might get away with simply changing the permissions (which you could do under the live-dvd environment).
But again, I would only try that on a copy of the drive. My understanding is that playing around with a failing disk (even a scan) increases the risk of changing bits here and there and making a recovery more difficult.
Haha perfect. In the middle of a scan right now. 🤦🏼♂️