Same problem here. Lot used to be a vet clinic that I would also live on. Currently no mods installed. It has never been a residential rental. Changed it back from vet clinic to residential now that I am finally supposed to be able to officially live in my business venue. But I cannot assign my home lot to my small business. Please fix this! This was the whole point of buying the new pack.
Resolved the issue by saving both my houshold and my plot to the library, starting a new world and placing both in them. Now assigning my homelot to my small business worked. There really seems to be an issue with lots that have ever been anything but residentials, like vet clinics or residential rentals.
