Mini Lights on Pre-lit Christmas Tree Don't Work?

I have a pre lit tree, about 6 yrs old. I absolutely adored this tree because it had globe lights on it as well. However, last year the mini lights gave me trouble, so I thought I would salvage the globe lights and remove them. Only problem, the mini lights were put on "after" so I had to remove all of them. I planned to check the mini lights and reuse the tree by stringing it myself. Well, the mini lights won't burn when I plug them into the outlet. None will work (about 6 strings). Any suggestions?

By JY