ODST Messed Up Achievement... Solutions?

So I just beat ODST on Co-Op... twice... I got all of the Achievements except the Costal Highway one and then obvious the three for beating the game on legendary. Sat through the credits and waited a few minutes and nada. This is pretty ridiculous we pretty much played straight through, gamertags never changed or anything. Any solutions? I don't want to keep beating it over and over again to no avail. I even redid the last level and nothing.ODST Messed Up Achievement... Solutions?
go to the select mission screen and it should tell you what ones you have and havent done on legendaryODST Messed Up Achievement... Solutions?
Yea it says Coastal Highway isn't done though we just beat it twice.
[QUOTE=''mmofnbs'']Yea it says Coastal Highway isn't done though we just beat it twice.[/QUOTE]

from the very beginning to the very end?
On legendary?
[QUOTE=''chaoscougar1''][QUOTE=''mmofnbs'']Yea it says Coastal Highway isn't done though we just beat it twice.[/QUOTE] from the very beginning to the very end?[/QUOTE]Yeah, you need to play the level as a whole in order to get credit for it as an achievement with coop, can't stop the game and then go back to it.
[QUOTE=''mmofnbs'']So I just beat ODST on Co-Op... twice... I got all of the Achievements except the Costal Highway one and then obvious the three for beating the game on legendary. Sat through the credits and waited a few minutes and nada. This is pretty ridiculous we pretty much played straight through, gamertags never changed or anything. Any solutions? I don't want to keep beating it over and over again to no avail. I even redid the last level and nothing.[/QUOTE]I was playing Halo 3 on Co-Op with my friend, he had to leave, so I went back to the save point we left off at and finished the game. When I didn't get an achievement for beating it, I figured out you have to do the whole chapter. I'm assuming it's the same for ODST.