In 4.24 I was having the same issue, idk about 4.25 Seems like I solved it by changing the hair width to something larger. Also I noticed that there are issues with the groom not doing what its suppose to if you don’t export properly using the docs here XGen Guidelines for Hair Creation | Unreal Engine Documentation. I was taking a shortcut by not completing this maya script stuff, at the end and I think that was ok, for 4.24.2 but then they patched to 4.24.3 and it became necessary.