Unity WebGL stuck on "0% Loaded" in Facebook instant games

No matter what I upload to Facebook instant games, it will not load the game I am left with a “0% loaded” message, though the game clearly loads in the background. This is even the case with a simple build just to display a sprite.

There is very little information on this type of error on the internet is this because Unity is not the best choice for developing an instant game for FB?

add new JavaScript script inside build

		//load assets here if necessary

and then include it in index.html manually:

//add this line
<script src="ScriptName"></script>

also if your game is WebGl build it will not work on mobile. for that you should use unity tiny or another engine.