I really do think your tree is suffering from lack of water at the roots, Most Maple (Acers) like a shade or half shaded areas, and the hot sun can toast the leaves, the tree struggles and after several attempts at growing new sets of leaves, it gives up as it takes a lot of energy to produce leaves or flowers.
My best advice would be to dig several holes around the root area, cut the bottom off clear plastic juice containers and cut the bottom off.
Insert the bottles into the holes (upside down) and backfill if holes too wide, get the garden hose out and fill the plastic bottles up several times, this way you know the water will be going to the roots, it is always a good idea to add loads of compost or animal manure into the hole when planting tree's Shrubs that are to be in the soil for a long number of years, this helps retain moisture and feeds the plant at the same time, by the way, every now and again when your watering the tree, you can add a liquid feed to help boost the tree on but, I would not feed it at all till you know it is beginning to regrow again, last thing this ;little tree needs right now is a boost of hormones, it needs to settle and start to grow roots and the extra water will hopefully start it on this way. hope this helps, WeeNel.
