Hi, I'm new to DDR and am having some problems understanding dance master mode. I've been playing for a week or so, and I'm in area C. There were a couple missions that I had problems with but I figured them out and passed them all. But no more missions are unlocking. I've gone through sections a and b and cleared all the missions I had left open. So now I've cleared all the missions I can but there are no more opening up. There are a lot of gray-lined boxes in b and c but I dont know how to get to them. Please help, thanks.

yeah ive been having the exact same problem....

It depends on which screen your using...
If your using the screen that has 3 songs pre-selected for you, then use the switch screen option, and manually select the songs, that are cut off, before they are linked to another box.