I am not sure of a specific problem, but I have experienced this, and unfortunately, learned to scroll all the way to the top of the page where a highlighted section states (usually but not always) what the problem is. My usual error is I put the place of marriage in the field for the date of end of marriage. It's usually something silly that I overlooked or forgot to enter like gender, or first name because I am too busy entering the date fields.
Another suggestion: Before you create a profile, do a quick check to see if there is possibly one already created, because when you get to that possible match screen and choose one, all the data you entered will not transfer to the original profile, and you will need to go back in once the profiles are linked and add the information/corrections that you have.