Hi Divya,
A complex issue.
After a Nov - 2015 update to Windows 10 my installation of FSX-Gold/Acceleration reverted to Demo mode and dropped out after 30 minutes.
I uninstalled FSX/Acceleration and re-installed (after PC restart) and got the usual
1311, 1722, 1603 as well as the activation error on start-up - 8-c0000006.
Also FSX had reverted to Demo mode with no product ID registered.
I did a restore to Nov 10 (update was on the 12th) and FSX now listed my product code but the program still gave the 8-c000006 error and dropped out after 30 minutes.
I have run the KB928080 app, several times, and reset the SLDL file but no changes, FSX-Acceleration still lists the Product code but remains in Demo mode.
I have posted elsewhere on this at Microsoft but no solution yet.
I prefer not to add a second account to the PC if possible to avoid.
Kind regards, best wishes for 2016
Keith Harris