I have a two person corporation. NJ says we missed a WR-30 payment from 1998. A judgement was made in 2003. We never received any info. Help

First thought the notice was fake but verified that it was from the Dept of Labor. This was for a (supposedly) missed WR-30 payment from 2nd quarter 1998. My tax returns only go back to 2000...different accountant, different bank. There was a judgement in 2003 or 2004 and a charge of $75 for court costs and the state claims we were sent a certified letter. It was never returned so they assume we received it. I never did nor have I had any notification of this until now. The amount missed was $877.76. To date the total with the interest is "With regard to your recent inquiry for a payoff figure on this judgment, please note that a remittance in the amount of $3,880.36 will be sufficient to liquidate the covered liability, subject to a final audit by our cashier’s office. This figure includes court costs and sheriff fees due in order to satisfy the judgment." Suggestions? Help?