I'm guessing you have a veiled cham. Hmmm.. First question where did you get your pothos plant? If you answer something like a hardware store probably take it out. Usual cases Lowes or Homedepot puts some fertilizers and pesticides on their plants. If you can be certain that the plant is not exposed to chemicals take a close look on how much he consumes and his behavior. Those plants are great in usual cases but can be toxic if consumed in heavy doses, especially in young chameleons. They are great for their vines and easy care but just keep a close look. Usually its okay to have them. I have 2 in Diego's cage. He is loving those long vines!
New plants from the store can be loaded with pesticides and fertilizer. Take Sandra's advice about other snacks to tempt your cham with. Mine used to eat ficus and hibiscus like it was a weed eater.