I noticed I couldn’t get the tunnel working while doing some dev work. Using DEBUG=* it seems to be caused by localhost resolving to the IPv6 ::1 where n8n is seemingly only listening on IPv4 0.0.0.0.
The workaround/fix is to start with this env var N8N_LISTEN_ADDRESS=::
N8N_DEV_RELOAD=true N8N_USER_MANAGEMENT_DISABLED=true N8N_LISTEN_ADDRESS=:: ./packages/cli/bin/n8n start --tunnel