This happened to me once, a long while ago. Have you tried searching the forum for a solution? Pretty sure that whatever I did, I found it on here. I think it might have been as simple as to go to Edit Town, change the lot type to Residential and then back to Community. If that doesn't work, try editing the lot, deleting the building, and replacing it (if you're unaware where the rabbit holes are, go to Build > Community Objects and then scroll down until you find the building).