Since I don't know about your specific development, I can only speak to what I've seen as an appraiser and Realtor. Townhomes do not need to be on the approved list by FHA - condos do. So while your townhome may look like a townhome, it's probably actually a condo.
You can check to see if you association is listed as 'approved' on HUD's list of condos:
It may have been at one point and that's why some people have FHA loans, but then rejected by FHA for some reason now and thus the reason why you can't get an FHA loan on your place. Hope this helps!