Just to get the obvious question out of the way, are you clicking on the "View Purchaseable Properties" button in the real estate menu? If your household doesn't currently own anything the property listing looks empty when you first pull it up. (I ask because it took me a second to figure it out when they introduced the phone/real estate option).
Do your properties have any community buildings on them? Like a rabbithole (bistro, hospital, gypsy wagon, etc)? You won't be able to buy the lot itself if that's the case, though you should be able to invest in the business that's on it.