WebCheck performs strict TLS validation. It does not disable certificate verification just to make a target appear healthy.
Hostname mismatch
The certificate does not cover the hostname WebCheck monitored. Check the certificate SANs and the hostname configured at the TLS terminator.
Invalid chain
The server may not be sending the complete certificate chain, or the issuing authority may not be trusted. Install the correct intermediate certificates and verify the deployment.
Protocol errors
A TLS protocol error can indicate incompatible versions or ciphers, a misconfigured proxy or a failing secure endpoint. Review the TLS configuration without weakening verification.