Imported Google Group message.
Date:Tuesday, 29 September 2015 13:39:20 UTC+1.
We just tested with the latest version of FF (On Windows admittedly), and the edit button works, as does saving and updating a user. It may be specific to the Linux version (also, the button is a link, maybe click the text, not the button?)
With regards to the user creds not working - you will need to create the user, then reset the users password for them to have access.