IntelliSense is not working in SQL Server Management Studio

This may seem too short of an answer, but probably it's the solution to your Problem:

CTRL+SHIFT+R

Also, I found this: Troubleshooting IntelliSense (SQL Server Management Studio)

I had the same issue. Everything was enabled to ensure proper Intellisense functions, but didn't work. I realized I had SQLCMD mode enabled by default. Disabling it restored Intellisense functionality :)

You can try solution from these questions1 or questions2 and questions3.
Or please try these steps as below:

• Enable IntelliSense:
  • For all query windows, please go to Tools >> Options >> Text Editor >> Transact-SQL >> IntelliSense, and select Enable IntelliSense.
  • For each opening query window, please go to Query >> Intellisense Enabled.
• Enable statement completion: please go to Tools >> Options >> Text Editor >> Transact-SQL >> General, and check on Auto list members and Parameter information boxes.
• Refresh IntelliSense local cache: please go to >> Edit >> IntelliSense >>Refresh Local Cache or use the CTRL+Shift+R keyboard shortcut to refresh.
• Wait a minute or two for the Refresh to finish before trying again.