A7 like most game engines cannot handle IK-rigs. If
you use a rig to animate your character, animations
must be burned into the native bones.
This procedure is either handled by the export
plugin (an export option like "convert IK to FK")
or you must do it by hand in front of the export.
Don't ask me how to do this in 3DSmax. But there
should be such a function.

Missing bone weights in the lower editions only
affects the skin smoothness during animation.
It looks more stiff or robotic compared to the
PRO edition. Unlike the engine, MED always supports
full bone weighting.