A game that refuses to load is almost always caused by one of four things: a bad connection, a pending update, corrupted cached data, or not enough free storage. Working through them in order fixes most cases in a few minutes without touching your account.
Fully close the game from the recent-apps list rather than just backgrounding it, then reopen it. If it still hangs, toggle Wi-Fi off and on, or switch between Wi-Fi and mobile data to rule out one network. Restarting the phone clears stuck background processes and is worth doing before anything more involved.
Many games refuse to start when a mandatory update is pending, so open your app store and update the game, and install any waiting system update too. If the game loads for no one, the servers may be down for maintenance — the developer notice or the official social account will usually say so, and waiting is the only fix.
On Android you can clear the game cache in Settings without deleting saves, but do not use Clear Data, which wipes local progress. On iOS, offloading the app keeps documents while removing the binary. Reinstalling is the last resort: bind your account to an email, Google, Apple or platform ID first, or unbound local progress can be lost for good.
Does clearing cache delete my game progress?
Clearing cache normally does not, but Clear Data does. Only clear cache, and bind your account before trying anything that removes app data.
What if the game still will not load after reinstalling?
Then it is likely a server, region or device-compatibility issue. Check the official announcements, and try a lightweight browser game meanwhile since those need no install.