1,check amount is incorrect, or has not been provided.
-How much did you paid? If the kid's I-485 is filed together with one of parents'I-485 filing, the fee is $635. If it is filed separately, the fee is $985 (no biometric fee for kid < 14).
See:
我resubmit小孩的485和131時,申請費應該是多少?網上說和父母一起遞是635,
現在小孩重新遞的還算不算單獨遞。
-I think it is counted as 單獨遞. But if you paid $985 originally and USCIS said this amount was incorrect, then your new filing is not counted as 單獨遞, and you just need to pay $635.
如果算單獨遞是不是有些表格要重填?
-No. Send the original documents back with correct payment.