Sometimes we can select the animation type sometimes it appears greyed out
It's not even about artboards being the same size. It works with different size artboards also. Why it doesn't work sometimes seems arbitrary
As we haven’t seen a response to our question in three months, I’m marking it as inactive. Please do feel free to file it again if you still want this feature!
AdminCorey Lucier (Adobe) (Admin, Adobe) commented
Please elaborate. There are certain animation types that don't or can't apply to sub-elements currently, just artboards for example, like auto-animate. Same for timed transitions. So these are grayed out when not applicable.