UE4 - FBX -Blender not exporting animations I just cannot export blender animations to FBX format

they do not play in FBX viewer
they do not appear in Unreal
no import options are displayed in the FBX import dialog

I tried exporting selecting the object, the armature, then both
also tried different options in the FBX export




edit :
I created another test scene that works, and I noticed that the scene that contains the animation that fails has an NLA displayed in green
how do I remove this ?
apparently a bug in blender 2.9
being investigated