I am having this same problem and came here to write this message. When importing a site from Relume (small, with 9 pages), the Builder Import hangs forever (see image). In my case not even the home page is imported as I continue to see the Official starter project in the background. I tried:
logout/login to relume, Webflow and the Webflow Relume App
Reinstall the chrome extension
Delete the Webflow project and start with a new one
Any suggestion?