FFnet has made changes over the weekend that broke FFF for everybody. I hope to be able to fix it, but there are no guarantees.
To the best of my knowledge, if you saved everything in the libary directory, unzipping it as a directory and then adding that dir to Calibre under Library -> Switch/create Library should work. Worst case, you add all the saved ebook files to a new library.
But that is as much as I know about it. You'll need to use your google-fu or ask over in the
Library Management sub-forum for more help on libraries.