What should I do when I fail to download while the device indicates that download has been started?

Please reboot your device.

Connect to LTE, 3G, 4G or Wi-Fi network, clear cache of “Google Play Store” and “Download Manager”.

1. Go to Settings > Apps
2. Tap “All” to show all apps on the device
3. Tap “Google Play Services” and “Apps”, then tap “Clear Data” and “Clear Cache”
4. Tap “Download Manager”, then tap “Clear Data” and “Clear Cache”