I created a simple animation, where a rectangle moves diagonally, and goes from blue with 100% alpha to green with 0% alpha. The colour transition is visible in the lottie export, but the transpacency is not. https://lottiefiles.com/share/viod5iif

I created a simple animation in Animate CC, where a rectagnle moves diagonally in a scene, using a shape tween. In the exported animation, the rectangle also rotates, but only in the preview. When I upload it, the animation is correct, and the preview also becomes correct. https://lottiefiles.com/share/clymfmsn

5 layer classic tween animation... only one frame rendered.