We have the same issue here: Some users can't establish connection to Cloudflare - #3 by djaho
We are currently trying to resolve this with Cloudflare Support, but the same as you, we can’t reproduce the issue on our side, so we have to ask users to run commands for us and provide us with the output.
When we finally found a user willing to execute a few commands for us in their Terminal we made some progress and wanted them to run a curl command to see the output of the SSL handshake. But after asking the user to run the command, they said that the issue went away on their end. A similar thing happened with some other users. The issue happened and then after some time (a day, two it went away). But then other users started reporting the same issue.
I believe that this issue is still happening for some users (they probably didn’t notice it yet), so it is just a matter of time when someone reports it again to us.
To help us both resolve this issue, I ask you if you can be so kind and ask one or more of your users which are experiencing this issue to run the following curl command in their Terminal (if they are on the Apple Mac devices, which come with curl pre-installed):
curl -svo /dev/null “https://app.lemlist.com”
This will output a lot more info about the connection and if you can get that output from your users and either paste it here (anonymized of course) or send it to Cloudflare Support, this will most likely help them figure out what went wrong there.
If there is anyone on this forum on Comcast and experiences this issue (or knows someone who does) with the original poster’s domain, then I would like to politely ask you to run the before mentioned curl command and provide us with the output. This will help greatly.
If not, I guess I will just have to buy a plane ticket, go to the States and try this out by myself