"Couldn't upload to your FTP server"

[teefers (Doug Bennett)]

Have a look at this post

RW8: Can't export or publish in local folder?

Try exporting your site to a local folder. If that works then use an ftp client to update. That will buy you time to figure out what’s going wrong with RapidWeaver publishing. Here’s a kB article on fixing ftp problems, in it is information on getting log files. https://help.realmacsoftware.com/rapidweaver-troubleshooting/how-to-fix-ftp-publishing-issues