Duplicati has a feature that tests the log-in procedure with your backup system. Was your FTP server able to accept Duplicati's attempt to log in? I've not found a support forum for Duplicati either, but there is a Google group that may be able to help you - https://groups.google.com/forum/?fromgroups#!forum/duplicati
A feature I've noticed is sorely missing in Duplicati is some kind of event log. I've set Duplicati to wake my computer every Friday night and run backup for my selected files. There is no way within Duplicati to confirm this has happened. I have to go to my backup location and see if the new files are there. This problem is compounded by the fact that sleep mode on my computer is not working well. Tonight I'll be doing my usual backup and will keep the computer on all night. I'm not confident yet in Duplicati's ability to run automatic backups, which is what I'd really like to have.