Sparse Disk Image Bundle won't mount disk after encryption
I have an encrypted Sparse Disk Image Bundle. For years I've been able to decrypt it, and once done it mounts a disk on Finder. Within that disk I have all sorts of important folders and files including tax information and other sensitive personal information. However recently when I enter the correct password, nothing happens. I can't see the disk being mounted in Finder, and thus can no longer access my critical files.
Additional details / things I've tried:
I'm running MacOS Monterey, v12.5.1. I have all file types turned on to show in Finder->Preferences->General->Show these items in the desktop. I know I'm typing the right password (it prompts me again if I enter the wrong password). Ditto on the Locations for the Sidebar. I have enough space on my hard drive to support the decrypted files (the Sparse Disk Image Bundle is about 600 MB and I have about 600 GB available). I've also tried simplistic things like rebooting, etc. but all to no avail.
One odd things that I noticed a few months ago was that I got a warning message about that file, something about that disk might harm my computer or something. I didn't know what to do when I got that, there's no reason I should have gotten the message, and for a while it kept decrypting just fine so I ignored it and the message never came back. But now, nothing happens when I when I decrypt the file.
Help? These are very important files and I really need to get them back! I'd appreciate any suggestions folks might have.
Thanks much.
MacBook Air 13″, macOS 12.5