For security reasons I need to disable the possibility in form the user to change his email. Once set it can't be change. How can I do this?
The problem was that we had an extension that override the user model/controller/view, example: social login, and because we decided not to use it we Disable it in the advanced settings.
Because it was disable, the list of users was not showing in the back-end, but I could create a new customer, yet in the New customer view the Addresses were not showing either.
So, we activated all the extensions again and suddenly the customers list appears. So like this we found out which extension was breaking and fixed it.