This Chrome message generally indicates the TLS handshake failed at a fairly early stage — before certificate details were even exchanged — often pointing to a protocol version or cipher suite mismatch rather than a certificate content problem specifically.
Diagnosing further
Check the specific underlying error code Chrome shows alongside this message (often visible by expanding the error details) — it typically maps to one of the more specific errors covered elsewhere in this category (ERR_SSL_VERSION_OR_CIPHER_MISMATCH, ERR_SSL_PROTOCOL_ERROR), each with its own more targeted fix.
What Chrome's specific wording for this error indicates about the underlying cause
This particular Chrome message generally indicates a protocol-level failure (an SSL_PROTOCOL_ERROR or similar) rather than a certificate-specific trust or validity issue — the site couldn't complete a TLS handshake at all, distinct from a certificate being present but untrusted or expired.
How to determine whether the server is actually running HTTPS at all on the expected port
Testing the specific port directly with OpenSSL's s_client reveals immediately whether any TLS service is actually running there — if the connection fails to even begin a TLS handshake, the issue is that nothing is listening for HTTPS on that port, rather than any certificate-specific problem.
What the underlying Chrome error code reveals when you expand the technical details
Clicking to view the technical details on this Chrome error page reveals the specific underlying error code (like ERR_SSL_PROTOCOL_ERROR or ERR_SSL_VERSION_OR_CIPHER_MISMATCH), which maps directly to the more specific troubleshooting guides covered elsewhere in this category.
How this generic-sounding message can actually stem from several different specific causes
Beneath this one generic Chrome message can lie a genuine protocol negotiation failure, a completely non-responsive server, or a fundamental network connectivity issue — expanding the technical details, as covered elsewhere in this article, is necessary to determine which specific underlying category actually applies.
A final note on building a personal reference
Bookmarking or saving the specific, more detailed underlying error code once you've identified it helps you or your team recognize the same specific issue faster if it recurs, rather than needing to work through this generic message's full diagnostic process again from scratch.
What the full range of underlying error codes this generic message can represent
Beyond a protocol error, this generic Chrome message can also represent a version/cipher mismatch, a connection reset, or several other distinct underlying TLS failures — expanding the technical details is always the necessary first step to determine which specific, more actionable error code actually applies to your situation.
How to systematically work through each possible underlying cause
Starting with the most common and easiest-to-check causes first, confirming the server is reachable at all, then checking for a protocol-level issue, then investigating certificate-specific problems, generally reaches a resolution faster than investigating causes in a random or assumption-driven order.
A quick closing checklist
A quick closing checklist covers expanding the technical details for the more specific underlying error code, testing directly with OpenSSL for additional diagnostic detail, and checking whether the server is genuinely running HTTPS at all on the expected port.
How this specific Chrome message has evolved in wording across different Chrome versions
Chrome has periodically refined the exact wording and presentation of this error across different versions, though the underlying technical error codes it can represent have remained largely consistent — the diagnostic approach covered in this guide remains valid regardless of the specific Chrome version showing it.