Mixamo Animation Retargeting

Hi
Thanks for the great plugin
It plugin was working for me last week, but now “Retarget Skeleton Asset” menu is greyed out.
I suspect it is because, the skeleton names are importing as :
mixamorig_Hips
mixamorig_Spine
Where as a week ago they were importing as :
Hips
Spine
I find this strange because the source fbx is the same (Downoladed directly from Mixamo website).
Only difference if running UE4.2 now, where as be fore I was on UE4.19
Could it be my FBX import settings?
Any advice would be great, to get this plugin working for me again.