This happens when your phone has weak internet connection or the app can't reach servers. Check if mobile data or Wi-Fi works by opening a browser. Toggle airplane mode on and off to reset connection. If you see one gray checkmark, the message left your device but hasn't reached servers yet. Two gray checkmarks mean it's delivered but not read.
When media files don't load, it's usually about storage space or connection quality. Check if your phone has at least 500MB free space. Go to app settings and switch from 'Wi-Fi only' to 'Wi-Fi and mobile data' for automatic downloads. Sometimes files expire on servers after 30 days, so older media becomes unavailable.
Outdated app versions cause most crashes. Open your app store and install the latest update. If that doesn't help, clear the app cache through your phone settings without deleting chats. As last resort, uninstall and reinstall the app, your messages stay backed up in cloud storage.
Verification codes might arrive late due to carrier delays. Wait up to 10 minutes before requesting a new code. Check if you entered the correct country code and phone number. If SMS doesn't come, try the call option for voice verification. Make sure you're not blocking unknown numbers in your phone settings.
Video calls need stable connection with at least 1 Mbps upload speed. Close background apps that use internet bandwidth. Switch from mobile data to Wi-Fi or vice versa to find better connection. Reduce number of participants, as calls with 5+ people require more resources from your device and network.