Alexandre,
I think that there is still an old user session stored in the database - possibly if P6 didn't close down correctly.
If you download "DB Browser for SQLite" which is a free utility from DB Browser for SQLite (sqlitebrowser.org)
Run the application then select Open Database & select the SQLite file that has the issue - Make sure you do not have this open in Primavera at the same time, as P6 does not like you making changes to the SQLite database when it is open.
Select the Browse Data tab, then from the Table Selection box select "PROJSHAR"
You should now see a list of all Projects that the database thinks are open in the application.
Go to Execute SQL & run the following SQL Query:
Delete from PROJSHAR where session_id NOT in (SELECT session_id FROM USESSION where delete_session_id is NULL)
If you go back to the PROJSHAR table (Hit the Refresh Button), you should see that these have all now been removed.
Close the database in the DB Browser application (before quitting the application) & open in P6 & see if it is still an issue.
Please note that as the SQLite is simply a file, I would make a backup copy of it before running any query against the database.
This should stop the annoying popup!
I have this function within a small Admin utility to allow me to clear locked user sessions, Clear Old Project Sessions & resetting passwords. Works for SQLite & MSSQL, but as yet untested against Oracle as I don't have an Oracle database to test against (but should work).
It's basically running the above query to clear old project sessions, but without having to download the DB Browser first.
Regards,
Steven