I have been trying to germinate some seeds from ACER PALMATUM for many years with success almost 0-2 out of 200 seeds, not enough to try again. If you have a way to do it, please share.
Acer Palmatum Germinating Seeds
I checked with one our local Master Gardeners who is fair more experienced in working with this plant. He suggested keep trying, this is very difficult to grow from seed, but he did mention the fresher the seed the better. I did find this website on growing ACER PALMATUM that you might find of help.