docs: add ARC troubleshooting note about NTP (#54718)

Co-authored-by: Joe Clark <31087804+jc-clark@users.noreply.github.com>

Author: joshjohanning

content/actions/hosting-your-own-runners/managing-self-hosted-runners-with-actions-runner-controller/troubleshooting-actions-runner-controller-errors.md

@@ -146,6 +146,10 @@ To fix this, you can do one of the following things.
         command: ["/home/runner/run.sh"]
     ```
 
+## Error: `failed to get access token for {% data variables.product.prodname_github_app %} auth: 401 Unauthorized`
+
+A `401 Unauthorized` error when attempting to obtain an access token for a {% data variables.product.prodname_github_app %} could be a result of a Network Time Protocol (NTP) drift. Ensure that your Kubernetes system is accurately syncing with an NTP server and that there isn't a significant time drift. There is more leeway if your system time is behind {% data variables.product.github %}'s time, but if the environment is more than a few seconds ahead, 401 errors will occur when using {% data variables.product.prodname_github_app %}.
+
 ## Legal notice
 
 {% data reusables.actions.actions-runner-controller-legal-notice %}