i also had this problem before. Updating to latest xiaomi.eu 7.4.6 rom + clearing/disable google app data backup/sync completely resolved this problem. :)
Can't update or download apps. I'm using latest xiaomi.eu rom 7.3.30. (experienced same problem with 7.3.23). Problem encountered after google play update itself to ver 7.6.08.N-all. Doesnt matter if using mobile data or actual wi-fi. The only temporary solution right now is to uninstall google...