Nc d-400 schedule s line 21 keeps giving error code when I put in my pension amount

Two possibilities"

1) If you have already claimed those $$ as being exempt under the Bailey Settlement  (line 20), then you cannot claim them again under the Uniformed Services exemption.

2)  If not #1, then the $$ amount on line 21 cannot be greater than box 2a on the 1099-R you entered in the Federal section   (or the Federally taxable amount of box 1 if box 2a was empty)... Also, that box 2a value must be indicated first as the NC Distribution amount.   Edit the 1099-R in the Federal section, and go thru the entire series of questions to make sure that NC distribution amount gets entered....it is NOT a zero.