It is important that your Facebook page is public and has no restrictions. When restrictions are in place, customers may experience problems logging into your social hotspot via Facebook.
Check the following on your Facebook page:
Go to 'Settings'
Then go to 'General'
Select "Everyone (13+)" under "Age Restrictions"
Make sure that "Country Restrictions" says "Page is visible to everyone". Adjust this if it says otherwise
Click on 'Save changes'
Finally, check whether there are other privacy settings that are not set to 'Public'. If you come across something that is not set to 'Public', please change it to 'Public'.