App Store Refuses To Open

You could try a start-up in Safe mode, and afterward re-start normally; this can help.

• How to use safe mode on your Mac - Apple Support

https://support.apple.com/en-us/HT201262

Good luck & happy trails!🌻🌤

You may need to try and see if by creating 'second Admin user' account

which could be useful in troubleshooting; be aware this gives full access

to the Mac. Other steps, not outlined in article, can perform more.

Then you could login to a second Admin account, to test the Mac; &

may choose to do other steps, to different destinations. ~Not sure but

you could start in macOSRecovery, use macOS Utilities, and repair Mac.

• How to Create a New Administrator Account on Mac OS - osxdaily

https://osxdaily.com/2017/07/17/how-create-new-admin-account-mac/

Doing this is only a step; at this point research, trial & error, is needed.

While doing this adds a possible way to access the Mac past safe mode

since none of the old content would be available to new Admin user.

• Backup disks you can use with Time Machine - Apple Support

https://support.apple.com/en-us/HT202784

Options to either attempt repair or move your existing Admin account

to the new user. If you have backup Time Machine from before this issue

you see if you could restore from that, in a new system.

An idea to try, especially if you have good backups, may be start in

macOS Recovery and re-install a new system. This should leave your

personal info & files intact; unless you erase that portion of content.

This angle could restore a working Mac system, and your original admin

user account should not be affected. There are steps and details in this.

If you hadn't already upgraded to newest macOS, that is not something

that should be done now. An older system that worked with your Apps

& had no other issue except the App store, can be replaced, w/ like-kind.

• How to reinstall macOS from macOS Recovery - Apple Support

https://support.apple.com/en-us/HT204904

And there are other ways to install macOS. Going into these, are tedious

with details that can seem sketchy. ~ You may need to start a new thread

in ASC, this one had been marked 'recommended' which may deter other

helper's participation.

Note the macOS Recovery exceptions; this may offer different options than

your Mac had been using. As Details in these articles Vary, outcomes do too.

Expect these paths to give sometimes conflicting direction, & may take hours.

(A good backup on external storage drive of your system (or clone of clean OS)

can be useful; these kinds of things one has to study, learn how to do.)

If you have a Time Machine backup on external drive, that may be useful.

What else have you tried, if any? This reply is more lengthy due to offline

considerations and need to be elsewhere.

Good luck & happy computing!🌞🌎