Hey so I am trying to make it so resources have double the amount to harvest. I have added to my GameUserSettings.ini,

[ServerSettings] HarvestAmountMultiplier=2

Restarted the server and no change in the amount we harvest. Tried adding it in Game.ini instead, still nothing. Any help on what I'm doing wrong would be appreciated.

On the server control panel from arkservers.io under the Advanced Settings tab use the search box and type "Harvest" you will see the exact same setting.

Harvest Amount Multiplier Higher values cause more resources to be harvested per strike.

Enter your value then click save and restart. These settings will be applied every time you reboot the server. Right now every time your shutdown and reboot the server the files are being wiped out (reset) because the control panel settings override the game file settings.

Same thing you were doing just use the control panel to do it.