I'd like to know about this as well.
By the way, were you using a Google Analytics extension?
I just ported some of my projects to GMS2 from 1.4 and it looks like the old analytics functions are now obsolete, but not sure if that was the case in the previous GMS2 versions.
The game I'm trying to use it on is one I made a couple of years ago in 1.4 and imported to GMS2. So your post seems to point to some sort of correlation. Maybe something to do with an imported game? Hmmm.
I originally tried using the built-in GMS2 GA support in the HTML5 tab and it worked for a few weeks, then suddenly quit working. I have beat my head against a wall trying to figure out what happened, but it did quit working right after I did the last GMS2 update. I've tried contacting YoYo about it but no reply from them for a number of days. They are good people and I'm sure they will get back to me when they can. Uh...I hope.
I then tried the "Easy Google Analytics" I found in the Gamemaker Marketplace. $4.95 and I couldn't get it to work.
Now I am considering using Game Analytics because they at least seem to offer pretty good documentation. I'm kind of a noob at all of this and just flail around in the dark until something works.