not sure what the exact problem is in your case, but i do know that these things are especially touchy. i have the same ones and depending on the flooring in the area im using them in, they work intermittenly, carpeted floor works fine, tile floor doesnt work at all. i've also heard that the ones we both have are not nearly as well made and user friendly as the offical sega ones..... that doesnt mean i'm gonna run out an drop 100$ on the official sega ones though. the game is fun but not worth that much to me.
so i would suggest:
try different things on the floor, a rug maybe, make sure the sensor is level and directly underneath the maraccas, and that you are holding both maraccas level and even. if that doesnt work, i have heard of people opening up their marraccas to mod them with LEDs and whatnot, maybe you can google a page that can help you take them apart and make sure they are OK....
hope some of that helps. it really is a fun game., when it works.