What is the flashing ! at the bottom?

I have a flashing yellow '!' on the bottom of my screen (above the store icon)
What does it mean?

it means you wont gain exp in that dungeon

Ya basically means your char is too high of level to gain any xp in that region, once you get to a higher campaign it will go away. Also could mean you have your no gain xp box checked in your options.

Thanks, That maks sense but I am not sure how I was supposed to guess that.

I was playing with my son in Forest Haven because he is only a level 3.