Some users can't establish connection to Cloudflare

Hi,
We are experiencing an issue where some of our users can’t connect to our CDN domain that is poxied over Cloudflare.
In Chrome, they receive the ERR_SSL_PROTOCOL_ERROR error message and in Mozilla Firefox, they receive the PR_END_OF_FILE_ERROR code.
The issue started appearing at the start of this week (2021-09-06) and it seems to be getting worse day by day (more users reporting the issue).

Both errors basically say that the secure connection failed or couldn’t be established. Chrome says “This site can’t provide a secure connection” and Firefox “Secure Connection Failed.”

Whenever we try this out on our side, everything works without any issues. Yet some users are complaining about not being able to connect and are sending us screenshots of these error messages.

We have already tried to disable the “Universal Certificate” on Cloudflare and enabled it back again to get a new certificate. But the issue didn’t go away.
We also disabled the Brotli compression (as mentioned in another thread here), but the issue didn’t go away.

Overall, it seems that mostly users from North America are experiencing these issues.

If we turn off the Cloudflare proxy for our domain, things work without any issues. But when we turn it back on again, the issues are back.

Does anyone have any idea what can be done (besides turning off the Cloudflare proxy)?

Hi @djaho can you share an example domain where you are seeing this error?

Hi @tobi, thank you for your reply. For confidentiality purposes, I can’t share the domain on a public forum. But I can share the Cloudflare ticket ID which I opened after also posting the issue here. The ticket ID is 2252930 and if you have access to it, you will see the two domains to which this error is related. You can then check which subdomains have the proxy mode turned on :wink:

Thank you

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We have responded to your ticket. Further communication on this issue will be deferred to the opened ticket. Hope that helps.

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