We typically see this type of error when the game has not downloaded all of the assets (content) that it needs before you enter the game. This is typically due to the internet connection being used to download the game.
If you are using wifi, you may wish to try rebooting your router or trying a friend's wifi for the initial download. Additionally, if you are behind a stringent firewall, using a proxy, or VPN, this may also be impacting the download.
Alternatively, if you are using mobile data, you will want to ensure that no other apps are using the data or downloading when you are trying to download the game. Also, if you are on a popular mobile network during peak times this error may also happen.