Google Analytics - "not provided"

Hello again,

we have a incredible big amount of "not provided" in google analytics.

So we dont really can see where our visitors are coming from.

Could it be that this is connected to the fact that we have the wordpress installation in a subfolder of the domain?

Or- Is google analytics maybe not setup correctly?
What possibly went wrong?

Would be nice if you can share some thoughts or insights about that topic.