As a number of users have already noticed, imports from Fanfiction.net are not working at present. Our coders have investigated, and it seems that FF.net is blocking requests from our servers. We're not sure at this stage whether this is specifically directed at us or whether it's a side effect of some other action; either way, it's not an issue that we can fix on our end. We're currently reaching out to the folks at Fanfiction.net to see whether we can resolve the problem; however, at present we don't have any ETA for a fix.
We apologise for the inconvenience - thanks for your patience while we figure out this issue!
ETA: This problem also affects bookmarking of works hosted on FF.net, since making an external bookmark involves pinging the site to check it's a valid url. We'll keep you updated as we figure out ways forward with this problem.