1098-t

My return was just rejected because turbotax states that the child earned credit was wrong and I needed to uncheck one of my dependents who is 18 and in college.  The software seems to have done this automatically and as a result my sons 1098-t info now states he is not eligible for the credit.  Why he is only in his second year.  Turbo tax says he is not eligible although he was in the first year and this credit is for four years.  What gives?