ERR_NGROK_318: You must reserve a wildcard domain for your account before you can use it to create endpoints - ngrok documentation

What does ERR_NGROK_318 mean?

ngrok returns ERR_NGROK_318 with this message:

You must reserve a wildcard domain for your account before you can use it to create endpoints.
Failed to create an endpoint with the wildcard domain <DOMAIN> for the account <ACCOUNT>.

Reserve a domain on your dashboard: https://dashboard.ngrok.com/domains/new

Where can I get more help with ERR_NGROK_318?

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