@jeraldweinstein that might be the problem: www-data is the group associated with the web server. The first “-” indicates that www-data does not have permissions to write.
I have 755 permissions for the whole WP folder structure, however my installation is only on a localhost for now.
Please note, I would ensure permissions are appropriate for a live environment. I have not yet researched best practice for security and permissions in a live environment so I am unable to provide advice.