Recently I encountered an issue when a user was attempting to login to Dynamics GP. After entering their user name and password they were receiving the error below which prevented access:
On this occasion I found to fix the issue I had to remove the users login from the ACTIVITY and SY00800 tables in the DYNAMICS database using the SQL statements below:
DELETE FROM DYNAMICS..ACTIVITY WHERE USERID=’<UserID>’
DELETE FROM DYNAMICS..SY00800 WHERE USERID=’<UserID>’
Replace <UserID> with the User ID in question.
After running the scripts the user could then access Dynamics GP without issues.
I hope this helps anyone else who stumbles across this issue in the future.
Thanks for reading
The Dynamics Explorer 
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