No error message,
after selecting import from 4 no past jobs show?
I noticed on your site that there were two versions, one for those who had ver 4 and one for people whom had updated, so I updated from within program
I'm now thinking that it has updated with older version?
If no jobs are shown when you press Import from version 4, that means for some reasons it is not recognized.
You can manually open in FBackup 5 the .fkc catalog files from the backup destination.
That will convert the jobs to version 5 and the backup jobs will appear in FBackup 5.