Same here.
Here`s what I did, and resolved the issue.
As my site is a little bit old, perhaps the analytics property was expired or not existant.
So I went to the plugins tab, and clicked on the reset option (next to the deactivate option).
Then I created a new property within google analytics.
Once logged into analytics, I went back to the plugin settings where I could re integrate, and enable the plugin by clicking on “pop ups blocked” option, and inserting my google code.
That’s it.