export asset as obj greyed out

i've imported an .ai file.  its a xmas bauble and personalised with a name.  i've edited the name and grouped all the objects together. i then select all and try to export it as a .obj file for 3d printing.  if no assets are selected in the asset export window the export as obj option is available.  as soon as i select an asset the obj option becomes greyed out and i cannot export.

can someone advise where i am going wrong please

no asset selected

with asset selected