Hi, could we see a pic of the cage?
I believe in three weeks he should be acclimated by now. We want to offer everything under the sun to get some feeding action to satisfy our own desire. I would personally suggest you to keep offering staple bugs and not worry about offering a variety of bugs right now. Crickets and roaches typically fit the bill as both are easily obtained. If this indeed a strike, you want to re-train him to eat what you know is good for him.
Things i would do.
1. make sure your husbandry/cage are spot on.
2. make sure he is hydrated.
3. have a fecal done on the next feces.
4. be patient.
Id also get in contact with who you bought this chameleon from and ask them what they were feeding and there care parameters. Id also ask if he was a picky eater.