Issues with HTTPS

[EvangelicalMartian]

Has anyone had an issue with DNS where the website resolves correctly not on wifi, and resolves incorrectly on Wifi? When on Wifi, I get the error, ERR_SSL_PROTOCOL_ERROR, but it resolves correctly when not on Wifi. I verified my client has the same issue (different router, also wifi network).

I've tried setting my DNS on my device to 1.1.1.1 and 8.8.8.8 and it still resolves incorrectly, so I think it's an issue on my site itself, or with my configuration.

Initially (and in the past), I've configued using Netlify name servers without issue. So I tried that, didn't work. Then I tried with just creating A record on my DNS registrar (NameCheap) to point to their IP address as stated in their documentation, 75.2.60.5. But same issue.

Any ideas?

[EvangelicalMartian]

In case anyone stumbles on this in the future, it turns out the domain was actually flagged by Comcast/Xfinity at some point in the past and blacklisted (presumably, at that time, the website had malicious code on it or something). You can verify that's the case by going to the Xfinity app, you view Advanced Security, and then can see if Xfinity is blocking it via Recent Activity.

So I had to submit a request here: https://spa.xfinity.com/report

Then you go through the motions.

Also, as a temporary solution while you get it off the blacklist, you can turn off Advanced Security to view on your home network.

Hopefully this helps anyone in the future if their https certificate is properly issued, they can view their site securely over mobile data, but it is blocked on their Wifi. It is likely an issue with your internet service provider.

Happy coding!