From what I was reading the error code normally happens when the profile is messed up for some reason. So to test that I want you to create a new local account on the system, just for a test. So name the account test if you like. Then log in with that account and see if the app store works.
For some people with this error who where signed in with a MS account they had to switch back to a local account and then the app store started working again.
Shane