There are a few issues that might get you stuck on the loading screen and you could attempt the following fixes.
1. You might have an unstable connection, try using an alternative internet connection to see if you are able to connect to the game.
2. Your Google Play Services might also be outdated, try updating your Google Play Services to the latest version.
3. There might be some issues with the cached files on your device, try clearing the cache on both Google Play and Crab War.
4. Your device might have same pending updates that are required, update your device and try loading Crab War again.
If you are still unable to load the game, please provide us more details such as your Country, Location and Internet Service provider in the support form provided.