Edit: Title is inaccurate now but can't change it (tldr: it was a setting on my router combined with probably a cert expiring, nothing to do with the modem).
Up until late Sunday evening (Oct. 11 2026), the same personal CODA56 I'd been using for the last two years was working fine with Xfinity. I shut down my network for the night and when I powered up on Monday morning, suddenly I couldn't do anything on the internet.
Signal looked fine, I could even ping internet addresses, but anything requiring Port 443 and TLS/SSL didn't work.
Which is basically the entire internet; any website you would go to, mail clients, Office 365, all use TLS/SSL. I verified that public http-only sites do work (for what that's worth), which means that DNS is also functioning, so it is either Port 443 being explicitly blocked or something broken/blocked about TLS/SSL other than the specific port.
Obviously called Xfinity support, they verified everything looked good on their end and in the modem, good signal, no errors on the modem. They refreshed the modem several times, I did as well in the Xfinity app, and I even did a factory reset on the modem in hopes of maybe clearing out a corrupt bootfile. Same issue
Had an onsite tech the next day and we confirmed that the problem was explicitly with the CODA56. His portable modem worked fine on my line, and from his wifi my devices had no TLS/SSL issues. Bypassing my router and plugging straight into the modem (pulling a public IP from Xfinity's DHCP), I had the same TLS/SSL issue, confirming that my endpoint devices were fine. It was the modem (Narrator: it was not in fact the modem).
Discussing with the tech, there seemed to be 3 possibilities:
- The modem had gone bad, period - It was two years old, he said Xfinity replaces their provided modems every two years, maybe mine was just end of life. Seemed unlikely to me, but possible.
- I was being blacklisted on port 443 on my modem's hardware address - More plausible to me, almost certainly not a person intentionally doing it, but some sort of script or AI automation flagging me incorrectly (my network wasn't even on overnight so it definitely wasn't doing anything suspicious).
- A corrupted or invalid boot config and/or firmware was deployed overnight on Sunday that I pulled first thing Monday - Also plausible to me, although the many resets not fixing the issue made me think the blocking was more likely. I didn't know at that time that a modem refresh from support or from the Xfinity app just sends the same config you already have, so if it's corrupted, it won't fix anything.
- Edit: or you know, number 4 - your troubleshooting was sloppy and it was your router settings the whole time.
I thought blacklisting was most likely and the tech escalated my ticket to the group that could check that. Unfortunately, his main contact was out of office, so in the interest of time, I just ordered a new CODA56. If my current modem was bad or I was blacklisted by CM MAC, that would get me back online. If the old modem wasn't being blocked, it was bad and I just toss it; if it was being blocked and got cleared when the contact was back in office, I had a backup.
Over-nighted the modem, hooked it up, good signal, provisioned it and had exact same TLS/SSL issue.
Called support yet again, refreshed new modem multiple times, no change.
And that is where it stands; no functioning broadband for 4 days, working 100% remote via a hotspot on a mid-tier Samsung phone and calling support daily. I've also opened a ticket with Hitron and they agreed it sounded like a config issue from Xfinity.
I'm hoping there are Xfinity people on here that can help get my ticket to the right group, or can determine I'm way off-base and know what the issue is, or even know how to get the CODA56 config and/ firmware packages corrected on the Xfinity TFTP node local to me (I have the Xfinity ticket number with details, just didn't want to put it in the initial post).
Thanks for any assistance