Usually, the subscription builds are available only for the final Octane releases, not for the test builds. In any case, we are going to release soon the next 3.08 plugin build, and in this case, I'll try to include also the subscription version because the 3.08 plugin is the only one that can work with Houdini 16.5. Should be a matter of few days.
Computer Graphics Software Developer
Octane plugin development and support: LightWave and Houdini