Chrome disabled TLS 1.0/1.1 outright and enforces certificate transparency, so it fails where older browsers still connect.
Chrome disabled TLS 1.0/1.1 outright and enforces certificate transparency, so it fails where older browsers still connect.
Open chrome://net-internals/#hsts and clear the domain's HSTS/security state, then Settings → Privacy → Clear browsing data → Cached images and files. If it still fails, the server is offering a protocol Chrome rejects.
Chrome has its own failure mode, but ERR_SSL_PROTOCOL_ERROR has a wider set of causes. The most common one overall is: The server only offers TLS 1.0 or TLS 1.1, which every current browser has disabled.
Enable TLS 1.2 and TLS 1.3 on the origin and remove the deprecated versions. On nginx set `ssl_protocols TLSv1.2 TLSv1.3;` and reload.
The SSL checker reads the live handshake: protocol versions offered, cipher suites, chain completeness and expiry. If it cannot complete the handshake either, the fault is server-side and not your browser.
Chrome disabled TLS 1.0/1.1 outright and enforces certificate transparency, so it fails where older browsers still connect.
Open chrome://net-internals/#hsts and clear the domain's HSTS/security state, then Settings → Privacy → Clear browsing data → Cached images and files. If it still fails, the server is offering a protocol Chrome rejects.
Chrome tried to start an encrypted connection and the server answered with something that is not valid TLS. In almost every case the server is offering a protocol version or cipher the browser refuses, the certificate is broken, or something on the network is intercepting the handshake.