SQL Server Intellisense does not work

Check all the below things.

1. In Sql server management studio editor, go to
Tools>Options>Text Editor>Transact-SQL>General>Statement completion
Enable - Auto list members
Enable - Parameter information

2. In Sql server management studio editor, go to
Tools>Options>Text Editor>Transact-SQL>Intellisense>Transact-SQL Interllisense Settings
Enable - Enable Intellisense
Enable - Underline Errors
Enable - Outline Statements

3.In Sql server management studio editor, go to
Tools->Options->Query Execution->SQL Server->General
Disable - By default, open new queries in SQLCMD mode
(If its already disabled then Enable it first>click OK> goto above mentioned location> now Disable it> open new query window)

4. Whenever you add / change any database object , press Ctr + Shift + R, it will refresh the cache which intellisense uses for sentence completion.