I have honeslty never even heard of this frog before, but the most productive way to breed treefrog is with the use of a rain chamber. Basically, you are trying to simulate the rainy season, which is when most frogs breed.
Take your frogs, usually better if done with a group of them, and place them in a large aquarium. In the aquarium, have a few inches of dechorinated water and several floating "docks" for the frogs to sit on. In the water, place a pump attched to a section of PVC pipe that runs up the side of the tank, and then elbows into another section of PVC that runs the length of the tank. This second length of PVC should be drilled with a series of tiny hole facing downward, so that when the pump is turned on stream of "rain" will fall into the tank and onto the frogs.
Generally, if the frogs are in breeding condition, they will begin to call and you should see amplexus shortly. I would remove them after a few hours if nothing is happening and try again another day.
Again, this is how most other treefrogs are conditioned to breed, so maybe it will work for your's as well. Do some research on their native climate before and during the months they naturally breed and try to replicate that before the rain chamber thing.
BTW, I'd love to see some pics of them. Good Luck.