I was asked to fill in box (D) the number in the box of my W-2.When I did an alert symbol (!).It does not allow me to move forward. What do I do?

Box "D" on the wage and tax statement requires an 8 number character to be filled in. After entering the number displayed on the W-2 wage and tax statement an alert symbol came up (!) and prevents me from advancing forward in completing the questions. What do I need to do to continue.