IntelliJ IDEA: Cannot import SBT project

1. Move to /your-project-folder
2. Run ./activator
3. Type idea . It will generate IDEA project.
4. Open (not import) File->Open.. project in IDEA.

I had this error when importing a new module from existing sources.

• On the right-hand side of your IntelliJ window, you will see a list of vertical tabs, open the SBT tab.
• Select the module that's causing trouble, right click on it, select "Detach external project"
• Try to import the module again.