You probably do not have to do a full cvar_default or cvar_reset, which resets all your settings.
Instead try this:
/run ResetView(2) SetView(2)
Explanation: WoW has 5 different camera presets which you can override using the SaveView() function. The active view is the one you have last changend into using SetView(). The camera following does not work while your active view is one that has been overridden. So to make it work again, you reset a view (using the ResetView() function) and make it the currently active view using the SetView() function. In the example above I used view 2, but you can use any other.
See also: https://warcraft.wiki.gg/wiki/API_SaveView