Hi I am having the same problem. I want to understand if we do the same thing or not so maybe we will be able to solve this together (but you know, we were supposed to be able to do this with iClone 7.9.. anyway)
I export the animated character from Iclone as HDF5 and import it to Marvelous Designer as avatar, then I simulate the clothing and export it as alembic HDF5 as well. I Import the clothes in iClone as accessories and apply the alembic simulation to them. When I press play in iClone everything is perfect, both body and cloth animation.
Then I link everything for Unreal use with live link and auto setup but only the character moves in Unreal, not the clothes which stay in T pose, while in iClone both the character and the clothes moves perfectly.
Do you have this same problem? What's your workflow?