The gateway is running but could not read the dashboard's static files.
This most commonly happens after an update leaves a stale install: the long-running gateway keeps executing the old install path and cannot read the dashboard bundle (the process does not hot-swap to the newly-installed version). It can also mean the web assets were never built (dev / first-run) — build the frontend and stage it into the package before starting the gateway.
Try restarting Kiro Crew. The exact restart step depends on your environment: if you installed it as a service use kirocrew service restart (systemd / launchd); otherwise stop the running kirocrew gateway process and start it again.