Sorry, apologies for your licensing problem.
The Octane license should be deactivated automatically in the computer when you close Houdini, unless you have activated it using the offline licensing feature. If you activate the license in offline mode, then you need to deactivate it from the Standalone in the computer that is using it to make it available in other computer.
Perhaps your problem is that you have the license activated in offline mode ... I am not sure. Anyway the next Octane build is going to have new tools to configure and view the licenses, and more fixes related to the new licensing system.
Computer Graphics Software Developer
Octane plugin development and support: LightWave and Houdini