Please post a photo or two of the frog and enclosure.

What are the enclosure temps both day and night?
What is the humidity and ho often do you mist the enclosure?

Do you de-chlorinate the water? Is the wwater tp or spring water?

You can try putting the crickets into a cereal type glass or similar bowl. Let him go in after them. The bowl needs to be slippery inside that is why I suggest glass but anything slippery and a rounded bottom works since the crickets can not get traction and jump out.
The crickets need to be no longer then the distance between the frogs eyes.