Be sure you are logged into Facebook through the blue Facebook login button.  Click the sync button located under the Facebook login button, to refresh your Facebook details.  If you are posting with SmartPost, and the albums are not autopopulating, click the Do Not Post field.  A list of the existing albums in the group should come up, and you can select the appropriate album.

Next, try loading one or two albums through the Manual tab, which can sometimes "jumpstart" Smart Post, then return to SmartPost.  Hopefully it can then pull up your albums.  

If you are still having a problem, I would suggest trying in an Incognito window.  This will clean up any lingering code attached to your webpage.  Open Chrome, then follow these instructions: