If you ever need to update the subdomain for your account (the URL you use to log in to Groove), you can do so directly from your account settings.
Any admin can update the subdomain under Settings > Company Profile.
Just type in your new name in the subdomain field and click Save. Voila!
Note: if you have a custom domain set up for your knowledge base, you will need to update your CNAME record to point to your new account subdomain.