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I got burned by this today so now it's a Weekly Dynamic, that way you'll know how to fix this.
If you login to GP, pick the company and then you get an error message that says:
Your login has been removed from the user activity file and you cannot be in the accounting system
You've got a client update problem. This happens when you've setup a client update and then the update file has been removed or deleted from it's location. I got burned when I disconnected our install drive…