Sure it was a new one? When delivered there should be a little plastic tab that presents the battery from making contact that you have to pull out first.
They take CR2032's and shoud last about a year on one battery.
I bought Mrs Q who is an Apple fangirl (she has an iPhone, an iPad, Apple Smartwatch, Air Pods and a Macbook) a set of 4 (along with holders) from the Empire of Evil for Xmas. She has put one on her car keys, one on my car keys which she borrows regularly and one in her purse. The fourth is spare. She did suggest to Youngest Q that she could have the 4th so we could keep tabs on her away at Uni but this suggestion was not well-received.