Your answer has to be the pinned one.
I had this issue because I have EU keyboard and there is no single ’ key, but only key combination which is not worked to show the debug HUD.
I tried to set the key bindings in Edit → Editor preferences… → Keyboard Shortcuts → Show AI Debug.
Thank you for pointing out the Activation Key setting.
Now I can setup the other numpad keybinds as my keyboard doesn’t have numpad too.