Hi rmub99,
Welcome to the Apple Support Communities. I understand you're running into an issue with your Touch Bar.
Do you see the same "Configure in: Extensions Preferences" alert when you try using the Touch Bar in every app, or does it happen in a specific app? Also, to verify, do you see any other options available on your Touch Bar, or only the alert about extensions?
You mentioned you haven't downloaded any extensions. Have you double-checked to see if one of the built-in extensions might be causing this? Try clicking System Preferences > Extensions, and then check out the different options in the left-hand column. The top listing for "All" will only show downloaded third-party extensions, so you may need to click through the other options like Actions, Today, or Finder to see which one seems to require attention.
You might also try to customize your Touch Bar to see if you can add buttons. You'll find the steps in this link: How to use the Touch Bar on your MacBook Pro.
I hope this helps with your Touch Bar!
Have a great night.