Getting ERR_SSL_PROTOCOL_ERROR for Comcast and AT&T

[ruslanpilipyuk]

Hello, we have been getting issues from customers that are using Comcast and AT&T lately, due to getting ERR_SSL_PROTOCOL_ERROR. I have tried to talk about it with a support of Cloudflare, however we got an following answer, which I am hesitant about:

By your description I would venture to say that those ISPs are likely blocking your address using DNS redirection, hence the ERR_SSL_PROTOCOL_ERR as the certificate on the block page won't match the real one.

My advice is that you try and contact the ISP directly regarding this issue.

Maybe some has any other ideas or tips on how to solve the presented error. We are using TLS 1.3 with SSL/TLS encryption mode is Full, while using Cloudflare managed edge certificate

[sjr]

What is the domain?

@ruslanpilipyuk

We are using TLS 1.3

If you have set the Minimum TLS version to v1.3 on the Cloudflare edge, you may have some older client devices that cannot connect. If so, try setting the minimum to TLS v1.2.

@ruslanpilipyuk

SSL/TLS encryption mode is Full

Use “Full (strict)” to ensure your connection is secured end-to-end.