ERR_NGROK_SHIP_APP_PULL_CREDENTIAL_REQUIRED: A private repository that publishes to ghcr.io needs a 'pull_credential_id' - ngrok documentation

What does ERR_NGROK_SHIP_APP_PULL_CREDENTIAL_REQUIRED mean?

ngrok returns ERR_NGROK_SHIP_APP_PULL_CREDENTIAL_REQUIRED with this message:

A private repository that publishes to ghcr.io needs a 'pull_credential_id'. Runners cannot pull the image without one.

Where can I get more help with ERR_NGROK_SHIP_APP_PULL_CREDENTIAL_REQUIRED?

Email support@ngrok.com and include the error code.