Permissions error on backup database

Hi,

When I try to save my settings on the Database Backups, I get

The directory supplied in Backup Location cannot be used as a valid directory. The directory /var/sites/a/alexsavillephotography.com/public_html/wp-content/uploads/ithemes-security/backups could not be created due to an unknown error. This could be due to a permissions issue.

The settings could not be saved. Please correct the error above and try again.

I’ve also noticed that I haven’t been getting any new backups stored locally or sent to me by email.

Any idea why I’m getting this? File permissions are 755.

Thanks

Alex