FB publish 2 and multisite

I’ve got this plugin working fine on my root blog: robinandrews.net but when I try to use it on robinandrews.net/devonmathstuition I can’t grant access rights.

I’ve set up a new app on FB, but it won’t accept robinandrews.net/devonmathstuition as a domain name. It will accept it as the site’s url though.

Any ideas?

https://www.ads-software.com/extend/plugins/facebook-page-publish/