Error: An error happened at: tables.php(32)

Hello,

I recently moved my site to a new server. I tried to use Online Backup and I keep getting this error:

Error: An error happened at: tables.php(32)
Undefined variable: db_prefix

I already changed the permissions on my tmp directory so I know it’s not that.

Thank you!

https://ww.wp.xz.cn/plugins/wponlinebackup/