You might not be doing anything wrong.
One of my females hasn't eaten hardly anything in the last month. She is basicly inactive but stays on the basking spot. She only becomes active when her mate comes out to torture her. lol. That's about every 3 weeks for a day or 2. But, he won't eat when he's out either. Another of my females I haven't seen at all for over a month. It's just that time of year.
The best tool to have is a weight scale. If they don't eat much but maintain their weight or gain then it's fine.
Sometimes we spoil our pets. We offer what they like best and they eat it when they're really not hungry. The first female I mentioned above will eat the couple newly shed superworms I offer in my hand from time to time but if I put them in her regular dish they'll be there all day. 8 months of the year she's a voracious salad eater but hasn't touched it in weeks either.
Don't get too tied to Hornworms. They have a very high moisture content and will cause really loose stools if fed too often. They're great for egg laying females in season though.