This is a matter of patience sometimes. Did you read instructions carefully on the devices site?:
https://devices.ubuntu-touch.io/device/jasmine-sprout/
Sometimes it can do the trick to repeat the installation, sometimes even several times..
In my case I didn't have to downgrade to android 9, but most of the cases it seems to be useful. Just try again, be patient and kind to yourself! 🙂
maybe you want to read reports in the forum first, there are always some good hints to find:
https://forums.ubports.com/category/92/xiaomi-mi-a2
good luck!