ERR_NGROK_813: Your message "MESSAGE"" is not supported by this version of the protocol: PROTOVERSION - ngrok documentation

What does ERR_NGROK_813 mean?

ngrok returns ERR_NGROK_813 with this message:

Your message "<MESSAGE>"" is not supported by this version of the protocol: <PROTOVERSION>.

Where can I get more help with ERR_NGROK_813?

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