So I downloaded Forge Island from Live today, and when I started H4 it asked me to download a title update, however my internet is pretty slow so I canceled the update and got signed out of Live. But when I try to start Forge Island on Forge or even War Games it sends me back to the title screen. The music even glitches and I hear the Infinity music at the main screen. So does Forge Island need the update? Or does it need Live? I miss Forge World from Reach 
It did the same thing to me. Just re-download forge island and it should work. Do the update, too, just in case.
You need the update to play. I had to download it.
The title update is required to play as it contains some of the data for the new maps, armour and weapon skins from the Champions bundle DLC. The update is what incorporates the new content into the existing maps (hence the almost 300MB title update).
Alright I’ll try the update and redownload Forge Island too. Thanks all of you guys! 
The huge update is downloading a new shared.map file. Just a fun fact for us people who understand how the halo engine works.