So first I want to say the lease is not necessarily recorded in the courthouse, it is most likely only a Memorandum of Lease which is next to worthless.
If the well is a newer well that is a horizontal well, it likely won’t be Diversified who owns it. The most common reason I find that checks stop coming is when the well changes ownership and the new owner is doing due dilligence on the title, they find problems and put everything in suspense. It is basically on you at that point to contact them and provide proof of ownership.
If I were you I would use information from one of the old check stubs to get the well name or API number and then use the DEP website to find the well. There you can view reported production and find the current owner and contact them to ask why you are not recieving a check.