I have an FBX animation file downloaded from DeepMotion that I can import and play just fine in UE 4.27 but when I import it into UE5 it doesn’t play at all. Importing the exact same way both times.
I had this same issue and may have figured it out? In the FBX import options under the Animation section there is a checkbox for “Import Bone Tracks”. Once enabled the animation is playing properly for me.