Dust the crickets every other day. Only offer a few at a time until they have been eaten (3 at a time). Offer food daily.
I would need to see the frog to judge the age at all but Amy is correct in that males won't start calling until they are a little more mature and the nuptual pad is showing.

If you soak the frog while cleaning the enclosure, try spraying a squirt of liquid calcium into it's soaking water. Frogs absorb through the skin and it's sometimes easier than trying to get them to eat a powdery cricket.Just be sure that if you use this method to use it at a very light spray.....too much calcium can be just as detrimental as not enough.

Also, change things up by offering appropriate sized chinks of earthworm/ night crawler as well. Variety in diet keeps them active & healthy! Just make sure your source of worms is a good one. Petco, Petsmart & Academy Sports stores carry them (NO worms with dye injections please!!!!!).