Garry's Mod Error

Hey Guys
I’m currently having a terrible error. I feel like I have been ripped off. I payed 10 dollars to not be able to play at all. The following error is occurring for me when opening Gmod.

Steam Error: No SteamUser.

  • Make sure that Steam is up to date.
  • Try restarting your PC.
  • Try Garry’s Mod -> Delete Local Content

Please let me know if you solve this bug!

I am running a 2011 Macbook Air. Thanks Guys, and please help!

http://www.facepunch.com/showthread.php?t=1231076

Its temp , chill.