I fell into the void of doom at spawn and now it kicks me saying Flying is not enabled on this server.

 

All I can say is try restarting both your computer and your Minecraft. Other then that I would say try contacting a mod. Good Luck I hope your problem is fixed!

 

Is this still happening? If so, try connecting with minechat. If you can't, pm a mod and I'm sure they can find a way to meet up with you in-game to tp you when you log in.

 

The anti-cheat was removed, you should not get kicked for flying anymore. If you are still getting kicked, PM an online mod to TP you to spawn.