MacBook Pro 13 will not recognize battery and will not charge after battery replacement
I assume this an old-style (pre-unibody) Mac with a removable/user-replaceable battery pack... If so, contact the seller; you could have been shipped a dud. If it's an aftermarket, non-apple product, you should also visually check to make sure it fits properly, and that all the contacts  are clean, undamaged, and seem to be connecting. As I remember from doing the same thing, some of those 3rd-party packs were less than perfectly machined.