Estoppel with existing tenant

[Eyong Agbortogo]

I recently purchased a duplex in Columbus and discovered after closing that the former owner had an estoppel in place with one of the existing tenants. Unfamiliar with how estoppels work so looking for insight on this as I would like to replace the estoppel  with a lease instead. Can the tenant refuse to sign the lease and chose to stay on the estoppel? Do they have legal grounds to do so?