Have you attuned them yet? What size houses - don't recall what the furnishing category for crafting stations is, but if your houses are on the smaller end check that your haven't hit the limit for that category. Otherwise I'm not sure - the last ones I had were from an event last year, and they placed ok.
I tried to place them in a vacant house, only items in the house were thing furnishings it came with (plants, trees, lights). I tried one that was attuned to a crafting set, one that wasn't attuned to any set. Both were not available to be placed in the house. They still are showing in my inventory, but can be placed back into a storage chest.