I'm sorry to hear you're running into troubles. I'm trying to understand your message above.. let me see if I can restate it properly:
* You have Paid Membership Pro on your site
* When you login with JFBConnect, the user is disabled in the admin area
* The user is disabled whether they already had an account or if they're creating a new one
That sound about right?
If so, can you double check that you have "Skip Joomla Activation" enabled in JFBConnect and/or disable activation altogether in the User Management area of Joomla. Beyond that, if you disable Paid Membership Pro, does the issue go away? It sounds like you're on the right track for disabling different features to see when things work. That's what we'd recommend as well to understand where the conflict is, which will help us narrow down and resolve things quicker as well.
You mention that the Facebook login button should show on your site, but I'm not seeing it. Even if it did though, there's only so much I can see from the front-end if the user gets automatically disabled.
Let us know if the above is correct and if you are able to locate a conflicting extension or setting that may be disabling the user and we'll gladly help get you going however we can.
Thanks,
Alex