Halo reach chalenge problem

For the daily chalenges i would do,ex. “Kill 180 enemies in any game mode in reach”, I would go to firefight. then when i press start and go down to chalenges i enter that to see my progress for that chalenge. I find the chalenge saying “this chalenge cannot be completed currently”. How can i get that off and start doing the chalenge?

If you are doing a custom firefight mode, you need to be playing on NORMAL or higher.

That worked. Thank you very much and now let us save humanity