did you check the requirements?
Requirements:
-You'll need to update your Cinema 4D to latest versions(R16.050, R17.053, R18.057, R19.053). Otherwise the plugin will not work and not appear in menus.
-Internet connection for activation, be sure that C4D and Octane will not be blocked by firewall and any antivirus software.
-Updated Nvidia drivers(most recents like 39x.x) with Cuda 9.1 - change driver versions if you have much trouble with current driver
OSX 10.12.4 | Intel 12 core @ 3.33 ghz | 128 gb ram | NVIDIA GeForce GTX 1080TI | Ubuntu Linux slave with 3x 1080ti