XML-RPC issue

Hi, I can't seem to add my multisite (www.ridersblogs.co.uk) to the wordpress app. Upon checking, it seems to say that xml-rpc is disabled and that there might be a plugin issue but I can't see one.

The site is setup with an admin account to access all blogs and then an admin for each subdomain. Ideally, I want these admins to login to the WP app (Android) and then it show their site. At the moment, it says login failed, generic error.

It used to work...any ideas are welcome!