ERR_NGROK_SHIP_CONTINUOUS_DELIVERY_TRACKING_REF_NOT_FOUND: Branch BRANCH does not exist in the repository, or the ngrok GitHub app cannot see it - ngrok documentation

What does ERR_NGROK_SHIP_CONTINUOUS_DELIVERY_TRACKING_REF_NOT_FOUND mean?

ngrok returns ERR_NGROK_SHIP_CONTINUOUS_DELIVERY_TRACKING_REF_NOT_FOUND with this message:

Branch <BRANCH> does not exist in the repository, or the ngrok GitHub app cannot see it.

Where can I get more help with ERR_NGROK_SHIP_CONTINUOUS_DELIVERY_TRACKING_REF_NOT_FOUND?

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