Why /gamerule (/gamerule doFallDamage false and /gamerule doweathercycle false) doesn't work?

[VERSION 1.8.9] Hi, why /gamerule (/gamerule doFallDamage false and /gamerule doweathercycle false) doesen't work?
When I changed that commands doesn't work, and I even try to restart the server, but nothing.

Please anyone gonna helps me? (I'm making a really good pvp server)

Bye.

Where? In aternos or minecraft? because in minecraft 1.8.9 there's

And for aternos?

I mean, how can I set on my server aternos the gamerules of toggle fall damage and toggle do weather cycle??????????

Nooooooooooooo, thanks!