Please try the following troubleshooting steps to address this issue:

• Make sure you have the most recent version of the game installed - check this by going to your app store and manually refreshing the game's app store page
• Make sure you are playing with wi-fi and not with mobile data
• Make sure your wi-fi connection is stable and strong (e.g. no public hotspots)
• Make sure you are not using any VPN or ad-block software which may interfere with the correct functioning of the game