Remove Background in Quick Actions

Do try the Safe Boot as Randall_2023 suggested and test The reboot normally and test again. The Safe Boot willl do the following:

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.

Have you tried booting into safemode rather than just rebooting? If not, try that.

Start up your Mac in safe mode - Apple Support

A properly functioning Remove Background Shortcut used as a Quick Action won't need Preview, as it can handle appropriate images independently by selecting them in the Finder.

The following Shortcut works on macOS 14.1. I have not tried it on any release of iOS which is for iPhones.

This Shortcut handles one Finder selected image, not multiples. If you want to process and remove backgrounds from multiple images, you will need to enhance this shortcut with a Repeat with Each block that encloses the Remove background from and the Save actions.

The following handles multiple Finder image selections and the Save action will prompt for a save location with each image. You can remove that if you want the resulting images saved to the original image location.

Shortcuts : New Shortcut : right-click and select edit. Add the actions.

Shortcuts User Guide - Apple Support

I dint do anything but upgrade to Sonoma and the remove background feature stopped working once I installed Sonoma. It stopped working on Preview too. It might work about 1% of the time now.

Where is this control panel you posted here?