Question about ODST

I have a question about Halo 3: ODST. Everytime I go into play campaign, it says I don't have a saved campaign game. So that means I have to play a level ive already beaten so I can get to the mombassa streets and look for a level I haven't done yet. Why is this? Is there a way to get to mombassa streets easily? I try the first level, but I have to go through a tutorial and and then most of the paths are shield doors and are off limits.

 

Have you beaten the game? Pretty sure that's how you unlock free roam..

 

wow thats gay... so i HAVE to complete a level ive already beaten to get to new mombassa and get a level i havent done? absolutely homosexual...

 

Coop and solo are different now, when you complete missions coop they don't save for solo, unless you go to replay mission.

 

You sure? I've only played one mission solo (uplift reserve to get Vidmaster: Classic) and I can do free roam.