Campaign Achievement issues

OK i know halo reach has been out for a while and nearly everyone has beaten the campaign mode a billion times, however literally 3 days after i purchased the limited edition i pre ordered i shipped to afghanistan for 7 months lol. I have an issues that im finding it difficult to resolve. i have beaten the campaign mode on legendary several times now including at least 2 full play throughs without stopping. i have the achievements for beating every level except somehow the first which makes no sense at all because you cant skip it and just start at 2. and also having beaten this multiple times on legendary in a solo campaign i have yet to be awarded the achievement for completing the campaign on legendary in a solo campaign. also the achievement for making an armory purchase i was awarded it and then it was taken away. i dont personally know anyone else with these issues but i have read a few forums and other posts with related issues. any information would be appreciated. Thanks.

> OK i know halo reach has been out for a while and nearly everyone has beaten the campaign mode a billion times, however literally 3 days after i purchased the limited edition i pre ordered i shipped to afghanistan for 7 months lol. I have an issues that im finding it difficult to resolve. i have beaten the campaign mode on legendary several times now including at least 2 full play throughs without stopping. i have the achievements for beating every level except somehow the first which makes no sense at all because you cant skip it and just start at 2. and also having beaten this multiple times on legendary in a solo campaign i have yet to be awarded the achievement for completing the campaign on legendary in a solo campaign. also the achievement for making an armory purchase i was awarded it and then it was taken away. i dont personally know anyone else with these issues but i have read a few forums and other posts with related issues. any information would be appreciated. Thanks.

make sure you did the begining cutscene on legendary or the achievment wont unlock