Hi,
It appears that the backup has been timed out or killed
Could you try to reduce the backup archive split size. This will split the backup into smaller, more manageable files.
To do this, open the ‘expert settings’ section of the UpdraftPlus Settings tab, and find the ‘split backups every’ option. Set this to 25Mb save your settings and run a new process.
If the issue persists, please ask your hosts/server admin to investigate their PHP error logs. These logs should contain more information on the exact issue that is causing the backup process to halt.
Kind Regards,
Bryle