After updating to 13.5.1, secured folder won't open

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

Barney-15E wrote:

Have you tried running first aid in disc utility on the image? I don’t know if that’s possible, but worth a try. I can’t check if it’s a capability right now.

I don't think it is possible now that I have had a chance to look.

But, you could try Open Disk Image from the File menu and see if that will mount it.

In Terminal you can try copy/paste this, leave a space, and drag in the image:

hdiutil attach 

If it is just rejecting the password, I don't have much hope in either.

Have you tried running first aid in disc utility on the image? I don’t know if that’s possible, but worth a try. I can’t check if it’s a capability right now.

What do you mean by a "secured folder?"

You can encrypt a disk image. Is that what you mean?