There are definitely some challenges with this. It is possible to convert your model to the new ConDoc 4 layers, but it will take a while to do and you will need to make sure that you’ve totally removed ConDoc 3 (including the templates, old layers, etc.)
Here are two options that might work:
Re-install ConDoc 3 and finish your project. Upgrade to ConDoc 4 after the project is complete.
Uninstall ConDoc 3 (remember to de-activate your license first), install ConDoc 4
Unfortunately we don’t have a quick v3 to v4 conversion solution for a project at the moment. Because we completely changed how ConDoc works in version 4, it’s unlikely that your old v3 layers and scenes will come through correctly into ConDoc 4; it’s best to ‘start clean’. It really will make a difference when you’re onto 4 though.