User authentication in Ubuntu 16.04
I clean installed the release version of Ubuntu 16.04 LTS, and all updates. I then added other users as administrators.
When an app, such as Synaptic for example, is executed the authentication menu shows all users, but the first (which is mine) will not initially allow entry of the Password. If one of the other Users is selected and afterwards the first (mine) is chosen, then the Password can be successfully entered.