Some users have come across an issue with version 3.00 which would not you them initialize standalone when using offline licensing. If you've come across a pop-up like this:
UPDATE: This has been fixed in version 3.01 that can be downloaded here, so if you are using standalone or a plugin supporting this version you may update and the issue should be gone.
Unfortunately the only solution is for you to disable offline authentication for the moment.
In order to do so you'll need to force Octane to re-authenticate, for what you'd need to remove the following file:
OSX: (you may have to use Finder's Go->Go To Folder... and type "~/Library/OctaneRender" - without the quotes - to get to that folder)
Once you've deleted that file restart Octane and when prompted for your OTOY credentials do not select the offline licensing mode.
We have solved this bug already in our development branch and plan to release a fix as soon as we can make a new release.
Apologies for the inconveniences.