You must have buildings in the theme for both the size and zone type you are using for buildings to spawn. For example, I am using an 'American Trailer' theme, which has houses of 2X1, 2X2 and 3X3 in it. I've noticed that if I zone commercial within that district, no buildings grow because there are no commercial buildings in that theme. Likewise, no 1X1 trailers grow, because there are no 1X1 trailer models within the theme. So you might need to check whether the neo theme contains commercial buildings, and also what size the buildings in that theme are.