There are different types of real estate taxes: those for owners, and those for residents. Some tax registers have one, some the other, and some have both.
Understanding which is which can be a vital clue to research your ancestors. If your ancestors owned real estate, that can prompt research into land records. If your ancestors were tenants, you can still check land records in case they owned property at a different time or in a different place. But if you cannot find them, that explains why.
Sometimes, it is hard to find out whether you are dealing with a tax for owners or residents. It can be necessary to do a literature search into the type of tax and the underlying regulations or laws. Careful reading of the records may sometimes also help to figure out in what capacity people were taxed.