fomo is available in most countries. There are certain regions where the app is not yet available due to regulations. Check the terms of service to see if your country or region is on the supported list: https://fomo.family/terms
If this doesn't apply to you, start by force closing the app completely and reopening it. On iPhone, swipe up from the bottom to open the app switcher and swipe fomo away. On Android, open recent apps and swipe it off screen.
If that does not work, delete the app and reinstall from the App Store or Google Play. Your wallet and funds are safe. Reinstalling will not affect your account, your balances, or your positions. Everything is tied to your login (Apple ID or Google Account). Sign back in with the same account you originally used.
If it still will not load after reinstalling, contact support.