Android One project promises fresh updates, right? Well, not always… E.g. I was stuck from October to nearly January without updates. If you also experience error with updates of your Xiaomi Mi A2 or Mi A2 lite phone, you should fix it manually. It says something like „Updates are temporarily unavailable. Try again later.“ But you could try it maybe forever without success. Fortunately, factory reset of your phone is not neccessary. I have found a fix on xda-developers forum.
“ Go to settings and then apps – all apps – upper right corner ‚ show system‘ – find ‚Google services framework‘ and clear cache. After rebooting updates are shown. „
You can clear not only cache but also data. Restart your phone is mandatory. After these steps, your phone should be able to reach the update server one again. And Android 9 Pie should be waiting for you. :)