Cannot Verify Identity of Device ... App Store and Macbook Pro

I was attempting to open an App (iReal Pro) and when it opened, I got a prompt saying "“iReal Pro” was purchased using the App Store on another computer. To use “iReal Pro” on this computer, sign in using the Apple ID and password used to purchase it."

This is the computer i used to purchase the APP. The app was working FINE until a few hours ago.

When I attempt to sign in, I get an error that reads "Your device or computer could not be verified. Contact support for assistance."

I get the same error when trying to sign into the APP STORE.

So, I changed my iCloud password and updated my password on all my devices.

I can sign into iCloud.com with no problems.

When I open SYSTEM PREFERENCES and click on iCloud and try to sign in, I get "You cannot sign in to iCloud because there was a problem verifying the identity of this Mac. Try restarting your Mac and signing in again."

I have looked up every article and discussion thread and tried all the tips but to no avail. I"m locked out of not only these Apps i need for work but also iMessages and Mail since i can't sign into iCloud on my computers System Prefs.

ANY help is appreciated. I'm in a bind and need this for work tomorrow.