Login with facebook just refreshing page

I’ve got a facebook app set up, which I’m already using for the fb comments plugin.

Trying to set this up for instant articles as well, using the same app ID /Secret.

However when I’ve entered the details and go connect to facebook, the page simply refreshes (code in the url changes though). If I’m logged out of facebook, I’m taken to the login box and which then fires back to the plugin page with the same login to facebook button.

I’ve set this up on another website, and it worked straight away though, same wp and plugin version. The fb app settings are the same, apart from domains being relevant to their respective websites. When I login to the second website I got all my pages in the dropdown, Including the one I’m trying to set up on the new website.

Only differences between the two websites is that the new website has a verified business page, I’m a page editor rather than admin, and the website i’m trying to set instant articles on is a sub domain of the parent website which the main facebook page is associated with.

Any ideas what may be causing this?

https://wordpress.org/plugins/fb-instant-articles/