When the business closed in 2016, that 2016 return should have been the final return filed for the business.
Look to see if that return is marked "Final" and if not, you may want to Amend it, with the only change being, "Final" return.
Sorry for your loss, also in 2017 when the partnership became one person, it is no longer a partnership, as must have two or more people as members.
The loan is considered now a personal debt.
