elythra doesn't work after defeating ender dragon in the overworld of a superflat world

I wanted to ride the elythra around.
I just fell to my doom.
I had recently defeated the ender dragon and went back to the overworld and wanted to ride the elythra

Make superflat world
You defeat the ender dragon and go to the overworld
make a command block going 100 blocks up and try to glide down on the elythra.