ERR_NGROK_SHIP_APP_ENVIRONMENT_BRANCH_REQUIRED: The 'environments[INDEX].branch' field must not be empty - ngrok documentation

What does ERR_NGROK_SHIP_APP_ENVIRONMENT_BRANCH_REQUIRED mean?

ngrok returns ERR_NGROK_SHIP_APP_ENVIRONMENT_BRANCH_REQUIRED with this message:

The 'environments[<INDEX>].branch' field must not be empty.

Where can I get more help with ERR_NGROK_SHIP_APP_ENVIRONMENT_BRANCH_REQUIRED?

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