ERR_SSL_PROTOCOL_ERROR does not identify it's cause a Sophos web protection.
Some pages are blocked by Sophos web protection due to SSL errors but there is no indication that Sophos is the cause of the blocking like when a page is directly blocked by the Sophos. It looks like a network error, or a google error or something else.
The same error with me we had zscaler, I spent time troubleshooting in zscaler and allow it already and still error SSL appearing and I bump to sophos central and I found it was blocked the sites there then confusion begins and questions why there is no sophos indication and it was blocked but it says err_ssl_protocol_error
I have the same issue. I blocked bandwidth usage and expected blocked message on navigating to netflix
This site can’t provide a secure connection
www.netflix.com sent an invalid response.
Try running Windows Network Diagnostics.