ERR_NGROK_SHIP_ENVIRONMENT_PREVIEW_NAME_NOT_ALLOWED: Environment ID is a pull request preview - ngrok documentation

What does ERR_NGROK_SHIP_ENVIRONMENT_PREVIEW_NAME_NOT_ALLOWED mean?

ngrok returns ERR_NGROK_SHIP_ENVIRONMENT_PREVIEW_NAME_NOT_ALLOWED with this message:

Environment <ID> is a pull request preview. Its name is fixed to the pull request number.

Where can I get more help with ERR_NGROK_SHIP_ENVIRONMENT_PREVIEW_NAME_NOT_ALLOWED?

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