trying to create DMG file, but get error message

I am trying to create a password protected, encrypted DMG file on my MacBook Pro (15-inch 2017 with macOS Ventura 13.7). I created two DMG files with the same name "_ Important MacBook Pro", but didn't like them. I erased both, unmounted both, and tried to create a third DMG file with the same name. Now, no matter what I do, I get the error message, "Operation failed with status 30: Read-only file system." Help. Thanks.