IntelliSense not working but it is enabled
There are number of possibilities where IntelliSense not working:

There are cases where the local cache used by IntelliSense becomes stale. Refreshing the cache is easy but not necessarily obvious.

There are two ways to refresh the cache: 


Hit Ctrl+Shift+R
Go to Edit -> IntelliSense -> Refresh Local Cache


If IntelliSense is still not working, then make sure you have IntelliSense enabled. To check this from the T-SQL Query editor window of the current database:


Go to Tools -> Options -> Text Editor -> Transact-SQL -> General -> IntelliSense
Go to Query -> IntelliSense should be selected
Also verify that the T-SQL Editor does not launch in SQLCMD Mode. To check:


Go to Tools -> Options -> Query Execution -> SQL Server -> General
Make sure "By default, open new queries in SQLCMD mode" is unchecked.
or Go to Query ->  SQLCMD Mode should not be selected



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