bcrodua

Hi,

That message is a PHP 8.3+ deprecation notice coming from WordPress core (wp-includes/kses.php), and it usually shows up after a big PHP jump (7.4 → 8.3+) when something passes NULL into code that now expects a string/array.

UpdraftPlus isn’t “the file throwing the notice”, but enabling it can trigger the upgrade screen flow where WordPress runs that code, which is why it disappears when you deactivate UpdraftPlus.

Please try to re-install your WordPress core files and make sure all old files are replaced/removed.

Thanks,
Bryle

Hi,

This usually happens because Google now enforces stricter sign-in methods (passkeys or phone prompts), which can block the authentication flow that UpdraftPlus uses. Being logged into Google in another tab does not automatically authorize third-party apps.

Please try the following:
• Use a new Incognito / Private window, log into the Google account, then start the Google Drive authentication again from UpdraftPlus.
• Temporarily disable passkeys or phone-only verification in the Google account security settings.
• Make sure pop-ups and redirects are allowed.
• Click “Having problems authenticating?” again and ensure the Google authorization page fully loads.

If it still fails, this is likely a Google authentication restriction rather than an UpdraftPlus issue. You can try a different Google account or another remote storage provider. If you’re on a paid plan, please contact us here so we can check further: https://teamupdraft.com/support/premium-support-form/

Best Wishes,
Bryle

Hi,

After upload, please click the “rescan local storage” link to refresh the backup list.

Let me know if issuer persists.

Thanks,
Bryle

Hi @aliamm

If you have a paid UpdraftPlus product (for example, UpdraftVault or Premium), please contact us directly via our support form so we can look into your account and logs securely: https://teamupdraft.com/support/premium-support-form/

For privacy and security reasons, account-specific checks can’t be done on the ww.wp.xz.cn forum.

Best Wishes,
Bryle

Hi,

That “Implicitly marking parameter … as nullable is deprecated” message is a PHP 8.4 deprecation notice, and in many setups it won’t break anything by itself, but it can break Google Drive downloads if the notice ends up being output into the HTTP response (for example when WP_DEBUG_DISPLAY / display_errors is on), because that can corrupt the API response and stall downloads at 0 bytes.

Also, try to reduce the split archive size to fix the backup getting stuck.

Best Wishes,
Bryle

Hi,

Can you share to us the backup log?
This log can be found in the Existing Backups tab of the UpdraftPlus dashboard.
If you cannot access the UpdraftPlus dashboard, then you can find the log file in the ‘wp-content/updraft’ directory via FTP or your hosts’ file manager.

Best Wishes,
Bryle

Hi,

These warnings usually mean UpdraftPlus is encountering temporary or incomplete files during the backup process, not that your backups are corrupted.

The unserialize() warning is often caused by non-standard data written by another plugin or theme, and UpdraftPlus is only reporting what PHP returns.
The filesize() stat failed warning refers to a .tmp file, which is a temporary archive that may be moved or removed while the backup is running or resuming.

Please try the following:
1. Update UpdraftPlus to the latest version and run a new manual backup.
2. Make sure there is enough free disk space and that wp-content/updraft/ is writable.
3. If backups are interrupted, keep a reasonable split size (e.g. 100–400 MB) and avoid running other heavy tasks at the same time.
4. You may safely delete old .tmp files in wp-content/updraft/ (do not delete completed backup files).

If the backup completes successfully, these warnings are usually harmless. If it fails, please share the backup log showing the final status.

Best Wishes,
Bryle

Hi,

Thanks for the details. The issue is caused by a PHP compatibility problem.

You are running PHP 8.4, but your UpdraftPlus version (2.13.12.1) is very old and not compatible with PHP 8.4. This is why backups never start, logs do not progress, and Amazon S3 tests fail. The Wordfence error confirms this with a PHP parse error in the S3 file.

Please update UpdraftPlus to the latest version, which is required for PHP 8.4 compatibility. If you cannot update immediately, temporarily downgrade PHP to 8.1 or 8.2, then run a backup.

After updating, test a manual backup and re-test the S3 connection. This is not a settings or theme issue.

Best Regards,
Bryle