Wd My passport won't show up on macbook

I recently got a new external hard drive for school, it is a 1tb My passport WD. It seems to work fine I just can't find it any where on my macbook. I have checked disk utility and there is nothing there, I have even plugged it into a windows os and it worked fine, I could access it and everything. But whenever I plug it back into any mac/macbook it won't show up. I would rather not go through the trouble af sending it back and looking for a new one, please help.