Hi,
I understand authentication in MXes works in a different way as they are Gateway devices.
You may apply this on VLANs not on SSIDs.
Screenshot attached for reference.
![Access Control.PNG Access Control.PNG](https://community.meraki.com/t5/image/serverpage/image-id/5579iA9032E0573E1FF06/image-size/large?v=v2&px=999)
Note : I have never tried configuring Facebook Login with MXes.
Regards,
Ajit
AjitsNW@gmail.com
www.ajit.network