I got this error trying to build a HTML5 app.
I’m using Instant Games extension in my “game.project” as a dependency.
This is how I’m trying to implement the FBInstant.
main.script
I don’t know what I’m doing wrong here. Any and all help deeply appreciated. Thanks.
The problem is probably with your index.html template. Are you using a custom template? You should be able to use the default template from builtins (and remember to configure it properly in game.project)
Thank you so much for your help. I was using the mobile template and changing the .html shell to engine_template in game.project solved the issue. 
