Character Accent Menu doesn’t appear anymore in macOS High Sierra

high sierrainternationalizationkeyboard

Firstly, this is for High Sierra

I've already tried this step:

Character Accent Menu doesn't appear anymore in macOS Sierra

Add a second language like French in Settings -> Keyboard -> Input Source
When I type defaults read -g ApplePressAndHoldEnabled in a Terminal
I got a 1
Go into Settings, Keyboard and make sure the Key Repeat slider is set to Slow and the Delay Until Repeat slider is set to Short.

Even if I restart the Accent Menu doesn't appear.

And this is my Mac:

macOS High Sierra | version 10.13, MacBook Pro (Retina, 15-inch, Mid 2015)

Like @TomGewecke said the only way I found to solve this bug was to create another user or to reinstall Mac OS High Sierra

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.

Thank you to @tom-gewecke's suggestion! Trying a different keyboard worked, functioning normally without this issue.

So it seems to be a compatibility issue between the aforementioned keyboard and OS, possibly other versions of both.