It should be that the version you are using is too different from the latest version, so the upgrade by OTA failed.

It is recommended that you use the full package method to upgrade:

1: Download the complete package of Xiaomi mobile phone card that suits you, and click the menu button in the system update interface to download the latest complete package.

Or/#, or this link/thread -790375- 1- 1.html.

Then put it in the folder of memory backup ~ ~ downloaded _ rom

2. Open the system upgrade-Settings-Select the installation package-Update now-Restart to enter the new system.

3. The upgrade is complete.