Windows routes HTTPS through Schannel, so a disabled TLS 1.2 registry key or an antivirus product that intercepts HTTPS (Avast, ESET, Kaspersky) rewrites the handshake with its own certificate and Chrome rejects it.
Windows routes HTTPS through Schannel, so a disabled TLS 1.2 registry key or an antivirus product that intercepts HTTPS (Avast, ESET, Kaspersky) rewrites the handshake with its own certificate and Chrome rejects it.
Turn off 'HTTPS scanning' or 'SSL/TLS protocol filtering' in your antivirus and reload. If that fixes it, add the site to the antivirus exclusion list. If not, run 'Internet Options → Advanced' and confirm TLS 1.2 and TLS 1.3 are ticked.
Windows 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.
Windows routes HTTPS through Schannel, so a disabled TLS 1.2 registry key or an antivirus product that intercepts HTTPS (Avast, ESET, Kaspersky) rewrites the handshake with its own certificate and Chrome rejects it.
Turn off 'HTTPS scanning' or 'SSL/TLS protocol filtering' in your antivirus and reload. If that fixes it, add the site to the antivirus exclusion list. If not, run 'Internet Options → Advanced' and confirm TLS 1.2 and TLS 1.3 are ticked.
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.