Issue with SSL Certificate for Custom Domain: ERR_SSL_PROTOCOL_ERROR

I am encountering an issue with SSL certificate for my custom domain. The SSL certificate seems to be misconfigured, causing SSL/TLS handshake failures.

It worked fine for around a year, now I get the ERR_SSL_PROTOCOL_ERROR error.

In the Koyeb admin panel it says that the domain is active, and it works on HTTP.

Now GlobalConnect and other ISPs like Telenor block the connection.

Does anyone have any experience with issues like this?

Update:
Also tried removing the custom domain from Koyeb. But the Koyeb domain is getting the same “This site can’t provide a secure connection”, “example.com sent an invalid response”, “ERR_SSL_PROTOCOL_ERROR”.

Maybe some issue with Koyeb?

I also tried to find a way to reach out to Koyeb support about this, but found no way to contact them, everything linked to the community forums. This seems kind of sketchy, as this is a critical service that is now down. An incident like this will loose you a customer.

Try to Remove SSL State

  1. Go to Start Menu and click Control Panel.
  2. Select the Network and Internet and go to Network, then Sharing Center.
  3. Click on “Internet Options” in the bottom left corner of the page.
  4. In the Internet Properties window, navigate to the “Content” tab and click “Clear SSL State.”

Or else clear the browser’s cache and cookies, also you can disable extensions. I have found one detailed solution also you can check here: https://certera.com/kb/what-is-ssl-certificate-not-trusted-error-how-to-fix-err_ssl_protocol_error/

This isn’t an issue with my system as it happens on my phone as well. I’m running macos so I couldn’t try the steps you provided.

A day after posting this the issue went away, but now a different SSL issue is back, I’m getting: “SSL_ERROR_RX_RECORD_TOO_LONG”.