We're trying to determine the cause, but it's difficult without access to the admin area or FTP credentials. Something very strange is happening though. I PM'd you earlier and mentioned an issue with your template. Disregard that as I got my posts confused.
As to things you can try now, we really just need to narrow down where the communication with Amazon is breaking down. The next bit of code to edit would be in the /components/com_jfbconnect/libraries/provider/amazon.php file. Around line 63 you should see:
$profile = $this->profile->fetchProfile('user', 'user_id');Please add:
JFactory::getApplication()->enqueueMessage( print_r($profile, true) );
That should add a new message above the "We were unable to retrieve your Amazon account information. Please try again." message that displays the information that Amazon is returning about the user.
Depending on what, if anything, that returns, we'll be able to decide where to dig next. Please add that code and leave it implemented.
If you get a white page on your site after adding that, it means there's something wrong with the code. Double-check it, or let us know, and we'll help investigate further.
Thanks,
Melissa