Adding license for SketchUp 2016 Pro

Does anyone have a trick up their sleve for adding classic license for SketchUp 2016 Pro? I have a valid license for this version but are not able to register the license after I installed it… The license-dialog seems to be unresponsive, no errors, just “silence”.
SketchUp support says that there may be a bug but that the version is no longer supported. They want me on a new subscription but I am reluctant as I only use SketchUp whenever I have a new project on my house…