On the wire
Ships with HTTP status 400, carrying "code": "RU-3002" in the response body alongside the human-readable error message. Existing fields are never replaced by the code: it is additive.
Common causes
- The target resolves to a private, loopback, or link-local address.
- An internal hostname that isn't reachable from the public internet.
- An unsupported URL scheme.
How to fix it
- Point the check at the public address of the service.
- For hosts inside a private network, install the monitor agent on a machine that can reach them instead of a public check.
Related codes
Still stuck?
Ask support and mention RU-3002: the code pins down the exact refusal path, so you skip the diagnostic back-and-forth.