You can check this document to get more information regarding authentication with cloud storage which might help you better understand the error you are getting. I am assuming you are running a Google Compute Engine VM and trying to connect to Cloud Storage from there using gsutil. If you find you are running an older version of it by checking the version, you can update it by running the update command. In case you are running the command elsewhere, please give the details of.
That said, I have also found this stack question which might have the solution required for resolving the issue you are facing.