ERR_NGROK_430: Another account is running an active tunnel on the domain DOMAIN

What does ERR_NGROK_430 mean?

ngrok returns ERR_NGROK_430 with this message:

Another account is running an active tunnel on the domain <DOMAIN>. You may not reserve domains that are actively in use.

Troubleshoot ERR_NGROK_430 with your AI agent. Connect it to the ngrok MCP server, then ask what caused the error and how to fix it.

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