Are you checking on the same server and database? (it has happened to me more than once)
Are you sure the spelling of the alias is correct?
Have you refreshed the Intellisense local cache?
Luis C.
General Disclaimer:
Are you seriously taking the advice and code from someone from the internet without testing it? Do you at least understand it? Or can it easily kill your server?
How to post data/code on a forum to get the best help: Option 1 / Option 2