In order to rule out any device-related causes, please try these troubleshooting steps first: 

• Force close the game
• Reboot your device
• Close any background apps
• Try a different internet connection, if available
• Check the App Store or Playstore for the latest game version
• Make sure your device's OS is up to date
• Have at least 2Gb of free storage

Clear your device's cache memory
1. Go to Settings > Apps (or Application Management)
2. Select Scrabble Go from the list of applications on your device
3. Select Storage then Clear Cache (warning: do not choose clear data)