I was hoping going back into 4.27 and adding a character with a beard (like Atoi) would update the mocap files and copying them would work, but it doesn’t appear to have updated anything.
Edit: This answer seems to have a clue: UE 4.26 Metahuman Hair, Eyelashes not moving with Metahuman Rig - #2 by storypilot1
The “binding asset” is blank for the hair that doesn’t move. I’m able to browse to binding assets that seem relevant, but once I select one, the dropdown goes blank again.
Edit 2: Finally got it working. See this thread if you’re still having issues: Metahuman missing Binding asset for some Groom asset - #8 by Rurrechuv I think it’s a problem with the MHC lighting project specifically.