I see you previously stated you have a 40 gal tank.
Keeping humidity in tanks is hard, but doable. If you're using a heat lamp, that also ruins humidity.
-Try using a more "wet" substrate that will retain moisture. Such as eco earth.
-Cover the screen lid with tinfoil/saranwrap/wet towel
-Mist daily
-Create a humid hide. Add eco earth or moss inside a hide and keep slightly damp.
-Move the water dish over the heat pad.