Hi RAJU.MSC, 1809 has been released globally . . .
With these major upgrades, the most successful method is to upgrade from the Windows 10 ISO - you download the ISO and then perform an Offline Upgrade
Click this link:
https://www.microsoft.com/en-us/software-downlo...
to download the Media Creation Tool (Click on Download Tool Now), with that you can download the latest Windows 10 ISO (Select Create Installation Media for Another PC), then choose ISO - do not choose USB
When the ISO file completes downloading
Then, double click the and then run Setup.exe from inside Windows File Explorer to begin the upgrade . . .
If you then get an error that Windows cannot be installed onto a USB flash drive, this may be related to a bug, where Windows 10 thinks it is Windows to Go running from a USB drive .. .
Click your Start Button, type regedit and hit Enter to open the registry editor
In the left pane, navigate to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control
Then in the right pane if this value exists - PortableOperatingSystem
Right click and delete it
Close the Registry Editor and restart your PC
Then check if the upgrade will proceed . . .