Can't use or sell small business venue

Probably my fault for trying to be too clever, but I tried to start up a second small business, so bought a second small business premises. Then as it didn't show up in the list to assign a business to, I sold the first small business I owned. Now I still own both small business venues, but I'm trying to set up a new business and it won't save if I alter lot 1 for the new business type and it doesn't list lot 2 to use. Nor can I sell either lot.

So I currently own a small business residential and two small business venues, but have no small business on either lot and I can't sell them to start again.

Any suggestions please? I don't use any mods.