Huawei
Choose or Add a Backup Account auf Huawei
EMUI links every cloud backup to a single Google account. If that account was never set, or a different one is signed in for backup purposes, files intended for Google Drive never leave the phone.
The backup account is managed separately from the main login you use for apps and the Play Store. It is possible to be signed into Google Drive with one account while EMUI keeps trying to back up to another, or to none at all.
To check or change it, open Open the settings ➔ Tap on System & update ➔ Tap on Backup & restore ➔ Tap on Backup account ➔ Choose an account or tap on Add account.
Selecting an existing account routes future backups to that Google Drive storage immediately. Adding a new account requires sign-in and Google's own permission prompts, after which it becomes available in the same list.
If storage on the chosen Google account is full, backups fail silently even with the correct account selected. In that case, freeing up Google Drive space or switching to an account with more room solves the issue faster than repeating the setup.