It sounds like your Inkscape's Python installation could be broken. Probably none of the extensions will work for you with this error message.
Did you update your Inkscape, or uninstall and reinstall?
Please try if uninstalling and reinstalling fixes the issue, and report back. If it does not, please open your file browser, and go to the Inkscape installation directory. There, try to find the /share folder, and the /extensions folder within it. Make a screenshot or copy a list of the files that are in that extensions folder.