A. This happens because the login session is expired and this can happen in the next situations:
1. If the Refresh rate from the PIP page is bigger than Session Timeout from Web Config (<add key="sessionTimeout" value="120" />). The Refresh rate must be always less than Session Timeout in order to keep the session.
2. If Application Pool (from IIS) is automatically recycling. You can check this in IIS - Application Pool - select Astrow - right click and choose Recycling.... There you shouldn't have anything selected if you need to keep the session.
3. If the IIS set to restart automatically during the night.
4. If the PC is set to restart automatically during the night.
