Users having problem loging in with Ultimate Facebook

Several Facebook accounts of my users cannot login with FB.
There is a button "Log in with Facebook" on the page: thaiquants.com

When they tried to login after clicking the button, popup shown up and that is it. No login. No FB avatar shows.
It just stop there.
Please help.

Please try this facebook account
Not Working
[Moderated]
comparing to this account
Working perfectly
[Moderated]
Thanks