Welcome to Android Central! Which device do you have, and which version of Android is it running? If it's Ice Cream Sandwich or lower, it's because Google officially dropped support for those versions.
We're getting a lot of these questions recently, several of the previous ones were a result of the version of Android on the device in question no longer being supported, as indicated by B. Diddy...
If you need additional help or have more questions or details to share, please join the site so you can reply in this thread. See this link for instructions on how to join Android Central.