ERR_NGROK_3106: The initial information required to authenticate with PROVIDER is invalid - ngrok documentation

What does ERR_NGROK_3106 mean?

ngrok returns ERR_NGROK_3106 with this message:

The initial information required to authenticate with <PROVIDER> is invalid.

Where can I get more help with ERR_NGROK_3106?

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