However, I am not able to register the serial number or reinstall the product through the add-on manager. As before, the box for entering the serial number does not exist. Reducing the size of the application window does not help
Either you had another program stealing the focus, or you haven't launched P3D from its icon, in case you have another add-on that starts P3D. Another possible cause of this, could be if you use the P3D Migration tool, which hacks P3D to look like FSX, so the Addon Manager won't find the sim dialog box function call that is located in different .DLLs depending on the version ( FSX, P3D V1 or V2 )
I have tried the registry hack by adding my serial number directly in regedit, but this does not seem to do anything either.
HKEY_CURRENT_USER\Software\fsdreamteam
With a string value called GSX containing my serial number.
That won't work, because it should have added a *folder* named GSX, with a string named "SerialNumber" containing the Serial.
You don't have to do it manually, because when you activated it the first time, a .REG file was saved in your Home folder (the folder with your name under C:\Users ), so you simply had to double-click on it to recreate the registry. Of course, assuming you saved that file from the previous reinstall.
Never mind, I finally fixed it by warping to a demo airport. Suddenly the serial box appeared as it should :-)
That's strange but, possibly, it allowed to regain the focus which was taken by another background app.
