This is a problem I found recently that was resolved simply – which might help others.
macOS Catalina Version 10.15.7.
Publii v.0.37.2 (build 13830) beta.
Art Gallery theme, v188.8.131.52.
Problem area: SFTP settings.
The SFTP settings appeared to forget the ‘Passphrase for a key’, when you change the ‘Passphrase for a key’. First time, it would re-enter the old passphrase, then subsequently just enter ‘publii-passphrase [sitename]’.
Of course, without the right passphrase, you can’t synchronise your local site to your live site.
My solution was embarrassing simple: close down then restart the Mac. When I restarted Publii, the problem was no longer present.