I'm having a problem where the Facebook JavaScript SDK isn't setting cookies on some machines, so my backend validation fails when trying to verify the cookie using my app's secret value.
I've got a demo app; the important files are:
The client uses the Facebook JavaScript API to log the user in and get their details, then posts these to my server. The server sends back the fbs_APPID which the client then displays. On some Windows machines (in all browsers) the server doesn't get the cookie it's expected. What's stopping Facebook from setting the cookie, and how do I go about fixing it?
The demo app is in Sinatra but our production app where we found the bug is Rails, if that makes a difference.