Check iCloud Status:

Visit apple.com/support/systemstatus first. Apple service outages happen. If status shows issues, wait for Apple to fix.

Sign Out and Back In:

Settings > [Your Name] > Sign Out. Wait a minute, then sign back in. Refreshes the connection completely.

Check Internet Connection:

iCloud needs stable internet. WiFi is better than cellular for syncing. Verify connection is working properly.

Toggle Sync Settings:

Settings > [Your Name] > iCloud. Toggle off the problematic service. Wait, then toggle back on.

Check Storage Space:

Settings > [Your Name] > iCloud > Manage Storage. Full storage stops syncing. Delete files or upgrade storage.

Update All Devices:

Ensure iOS and macOS are updated on all devices. Version mismatches can cause sync issues.

Conclusion:

Sign out/in resolves most sync issues. Full storage is a common but overlooked cause. Check Apple's status page first.