I know what this error means when applied to one of the LODs but not when applied to the High LOD:
https://www.dropbox.com/s/gdjzbecief76zmf/Screenshot 2017-05-15 16.14.49.png?dl=0
I have searched this forum and everything I have found references the Med - Lowest LODs, not the top. Ugh.
I have made all four LODs but did not bother uploading since the highest is rejected.
I exported as OBJ and imported, same problem.