I got the same issue , I use 5.5 import fbx never got issues, but i don’t know what happend or I click somewhere wrong… but the new Import Fbx option is not the same as before and got error no smooting group , also the mesh look ugly . ( I import in other project 5.5 is just normal ) .
I want to import as the first picture got no problem
but suddenly show like the second picture and the mesh got erro message no smoothing group …etc