We've identified an issue with LinkedIn vanilla profiles where the Interseller button currently does not show up. We've updated our Chrome extension to accommodate the recent changes and are in contact with Google to push this update as swiftly as possible. At the moment, it may take several days before we're able to push this update to all customers.
As an alternative, you can view the profile in LinkedIn Sales Navigator or LinkedIn Recruiter, use the Interseller button in the URL bar, or use LinkedIn's search view to import profiles.