Are you connected to Wi-Fi? Please, follow the next steps:
1- On the device, select Apps > Settings > Applications, Apps, or Application Manager.
2- Select All > Google Play Store
3- Select Clear Data and Clear Cache, if available.
4- Select Uninstall Updates
5- Select back to return to All applications.
6- Select DownloadManager > Clear Data and Clear Cache, if available.
7- Turn the device off and back on.
8- Access the Google Play Store, and try to download any app.