What to do if the MIUI system can't be updated on the Redmi 9T?

If you're facing issues with updating the MIUI system on your Redmi 9T, you can try the following steps to troubleshoot and resolve the issue: 
1. Ensure that your phone is connected to a stable and reliable Wi-Fi network. If you're using mobile data, ensure sufficient data and a stable connection;
2. Ensure your phone has sufficient battery level or connect it to a power source while updating to prevent interruptions;
3. Updates often require a certain amount of free space. Go to [Settings] >> [About phone] >> [Storage] >> [Free up]. Ensure your phone has enough free storage space for the update;

4. Go to [Settings] >> [About phone] >> [MIUI version] >> [Check for updates]. Sometimes, the automatic update process may not work correctly;

5. Sometimes, a simple reboot can resolve software glitches. Restart your phone and try updating again;
6. If none of the above solutions work, you can consider performing a factory reset. Before doing this, ensure you have a backup of your important data. Perform a factory reset by navigating to [Settings] >> [About phone] >> [Factory reset].
We hope the above information is helpful. If the issue still occurs, we hope you could submit your request or suggestions by going to [Settings] >> [Services & feedback], and wait for future updates.