Character Accent Menu doesn't appear anymore in macOS Sierra

Before upgrading to macOS Sierra, I really liked the Character Accent Menu by doing a long press on a key (for example, the character e) and being able to add an accent on it.

However, this functionality seems to not work anymore, and so far, I can't find out why?

Also, before, doing a long press on the delete button, would repeatly delete characters. Now, it is doing only one character deletion disregarding how long I'm pressing the key. So if I want to erase 10 characters, I need to press the delete button 10 times...

Also, I am not able to log off or shut down. When doing it, all applications are closed, status bar disappears but nothing happens. The dock remains here. I have no way to shut down or log out without doing a long press on the power button.

Is someone facing the same issue?

EDIT : Logging with a new user account or guest account fix all the problems. But I still would like to know what, in my user account, became corrupted during the upgrade.

I got the same issue after a recent update now, found the answer here and it worked for me. In Terminal type

defaults write -g ApplePressAndHoldEnabled -bool true

and then log out and log in again, this should fix the issue.

Found the solution. Go to System Preferences > Keyboard > Keyboard tab > Modifier Keys(bottom right corner). Now press restore defaults and see if that works.