Login with facebook not working

I have had an issue with ultimate facebook not logging in. I have deleted and recreated the fb app and my settings have been double checked. I tried disabling all over plugins and changing themes. Thought it may have been a multisite issue but this particular site is a stand alone install.
I am using Another WordPress Classifieds Plugin (AWPCP) which also asked for API and even though I have removed the keys from that plugin I am still getting the same failure. Have to assume that the classified plugin is the issue but it is necessary.
The plugin worked fine on an eCommerce store I created for a friend a few weeks ago and my set up has been identical.
At this point I have given up and now looking for an alternative plugin until one of the many internet forums can explain the issue and how to fix it.