Can't mount encrypted disk images after Monterey upgrade

I have a similar, but not idential, issue to to David Carlin's. I have an encrypted DMG that I've used for many years. It contains sensitive financial information. It worked fine on my old Mac, but I recently purchased a MacBook Air running OS X Monterey 12.1, and when I click on the DMG to open it, it asks me for my password as usual. I enter the password—it is the correct one—and nothing happens. No error, no nothing. It does not mount. I was wondering if there was somehow a password issue, so I typed in an intentionally incorrect password, and the password window reappeared, signaling that the previous password was incorrect.

The file is stored locally, and to be sure, I moved it to my Desktop and tried mounting it, but no dice. It does not appear in Disk Utility under any circumstances.

This is quite vexing. I hope Apple releases an update in the future for this bug.

Good idea. I will likely wait a bit to see if Apple fixes the bug in a future iOS update before going to the work of making new ones.

Three questions:

1. Are you happy with sparse disk images? I had tried them a few years ago and they behaved kind of squirrely so went back to the old kind.
2. Did you try mounting regular new disk images in Monterey, or just the sparse ones?
3. My Drobo NAS images no longer work with Carbon Copy Cloner. The backups always fail (and they worked great in Big Sur and earlier). Does anyone think the issues are related?

Thanks!

It seems like you found a solution using Terminal commands in Monterey. Another approach could be using the Disk Utility and Terminal from a bootable installer of an earlier version of macOS such as Big Sur. The Disk Utility (or Terminal) could mount the disk image and then a Terminal CP command could be used to copy the data elsewhere. Finally, the Disk Utility could be used to re-encrypt using a newer encryption version.

By the way, I've had problems with Monterey creating disk images from folders residing on external devices. The workaround (assuming sufficiently available storage) is to copy the folder to the internal (system) device before running the Disk Utility. Alternatively, the same bootable installer technique (with Big Sur or earlier OS) would work without the need to copy the data.

- Pie Lover

I have the exact same problem. All worked fine on earlier Mac OSs up through Big Sur, but not Monterey. Similarly, can successfully mount via Terminal. But would be nice to restore simple Finder open functionality. Would love some ideas! Thanks :)

"The disk image couldn't be opened

The disk image is corrupted"