Hard drive in external enclosure won't mount I'm trying to retrieve data from an old MacBook.

I've removed the hard drive, put it into an external enclosure, and connected it to my current MacBook.

This is the structure of the drive in Disk Utility:



I'm trying to access Macintosh HD, but when I turn the hard drive on only Recovery HD mounts. (Although I'm not able to eject it.)

I've tried mounting it manually and running First Aid.

Disk Utility sees how big the drive is, and how much of it is used, which gives me some confidence, but other than that I'm stumped.
I do a quick test before doing anything drastic. The app Mountain has a free trial. I'd load it and see if that will mount your drive. I had problems in the past with external drives not mounting. Mountain has been able to mount them.

Mountain is not a free app but they do offer a free trial. No subscriptions required.

Mountain is a menubar app. When you click on Mountain it should show you a list of all volumes connected to your mac. From there you can click on the Mount/Dismount button.