First off the frog isn't stupid because it isn't eating for you. Most likely your presence is stressing the frog which in turn will cause them to not eat.
You said you threw some crickets in there and he livened up but did you give him the chance to catch them on his own before placing your hand or tongs(whatever you're offering food with) in front of his face?
Get a small glass bowl and place the crickets in it. They cannot grip the glass so they cannot escape the frog making them easy pickings. Count how many you place in the bowl and then leave him be. Count to see how many he has eaten the next morning. I believe these are nocturnal frogs so food should be offered at night.
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