You probably had/have a "low beam tag" on your acct. A very annoying "tag" that is left over from when they had trouble with 129, and you needed a 24" dish pointed at it. Every time I do a "Dishing it up" and the customer has had HD for more than about 6-7 years, it comes up. Dish's computer will say you can't have a H3... It is a joke, exacerbated by CSRs that don't have a clue. The 129 issue was resolved last decade, but this "tag" is still on accts and a pain to deal with. The dumb thing is, you can hook a wing dish (129) to a Western arc hybrid LNB and it works fine, so even if the 24" dish was needed, it would be fine. But it is "outside the box" of Dish's thinking, so "YOU CAN'T DO IT"...
I spent hours on the phone with CSRs trying to activate H3s when they first came out, trying to figure this problem out. Most CSRs know how to deal with it now, and will remove the tag. I had more than a couple insist I couldn't do the install, so I hung up and called back and started playing "CSR roulet" until I got one that had a clue.
Anyway, that is what I think the problem is, you probably had it fixed by now.