HI guys,
Unless you have a subscription license, you will have to upgrade your version 3 licenses to version 4. This upgrade is free and can be done via these 4 steps:
Go to https://home.otoy.com/render/octane-render/purchase/
Select "Upgrade" in the top menu.
Click on "UPGRADE NOW" next to "Upgrade existing licenses to OctaneRender 4".
Select the licenses you want to upgrade and confirm.