Are you charging a separate fee for each of those five lots, meaning that one owner is being asked to pay five times what other owners pay?  If so, that may well be why that owner does not want to pay.  You may want to consider structuring your bylaws to address what constitutes one owner, bearing in mind that each owner should get one vote.  Do you want this person to have five votes?

I expect one of MARA's Board members may jump in here with a suggestion as to how their bylaws define a "parcel" for purposes of assessments.  Or use this forum's search function to find a Sept 2021 forum topic entitled "Voting: Multiple Lots."  Scroll down and look at the answers.

Your question doesn't make it clear if this owner has paid 5X dues in previous years.  Or is this a new owner?  If your current bylaws require that each lot is assessed separately, even if one owner owns multiple lots, and if this person (or other owners of multiple lots, if you have any,) have been paying a separate fee for each lot, it may be difficult to change the policy in mid stream.  

I'm afraid that doesn't answer your question as to whether separate claims must be made for each one.  If the lots all appear on one deed, it seems like separate claims would be redundant - but then, maybe that's also a hint that separate assessments are redundant.  I'll be interested to see what other respondents to this post think.