Many people, me included, wondered why the cloaking wasn't working. So I tried some things and came to a solution. The maker of the mod mentioned a short line of code:

[IndomRexRedux]
bCanStealthFirst=1
bCanStealthSecond=1

You need to add that to your GameUserSettings.ini in order for the cloaking to work.

(GameUserSettings.ini found here: ARK\ShooterGame\Saved\Config\WindowsNoEditor)

I hope I helped some people out with this.

Cheers,
Micr0