Google Optimize doesn't track active user session after activation on Ember app

I have inserted the page hiding snippet & the analyze-optimize snippet in the header. For activation, I have set Optimize to use the custom event activation. The Ember app will fire optimize.activate event every time there are changes

For my A/B experiment, I can see that the UI changes to the other variant. But, the Active visitors count in Optimize doesn't increment. It will only track the session when I manually refresh/reload the page