When I use the spawn egg, my mob doesn't spawn.

Hello all. I recently got back into MCreator.

As a result, i wanted to test creating a mob.

I made a creeper. For whatever reason, the thing doesn't even spawn. I don't know why.

When I go into creative, no matter the world type, it simply does not spawn using the egg, or at all.

It kind of flickers into existence and out when I right-click with the egg in my hand.

help.