If he is under the age of 24 and a full time student then you answered a question incorrectly when entering him as your dependent. The program would not ask about the gross income if he was being claimed under the Qualifying Child rules.
Go back and check your answers. Make sure that you indicate he is your child, verify his date of birth, make sure you indicated he lived in your home for the Whole year. you did NOT indicate the he provided for over one-half of his own support. That there was no one else in the home providing support. And that you did NOT check the box "not valid for employment" on the screen for entering his Social Security number.
If all of your answers are correct, then delete him as a dependent and re-enter.
