The forum has been alive for a couple of years with no issues. We get about 2k pageviews per day from about 100 unique users.
After an upgrade a couple of weeks ago, I started to get emails from users saying they can’t access the site. I have many users that are still able to access the site. The users with the issues are coming from different ISPs. They’ve cleared DNS cache. They’ve changed browsers.
What questions should I be asking to help troubleshoot the issue?
We are keeping the forums private, I’ll PM you the URL if you like, but I’d rather not have it on the open Internet. What part of the certificate is of interest?
It is Let’s Encrypt that is valid between Jul 29, 2021 and Oct 27, 2021.
Key size is 256bits
DNS name matches
The last time I upgraded I did a rebuild. Upgraded the server’s OS and everything.
A couple of users have relayed that they can’t get to the forum through their home routers, and when they try on their phones they get nothing as well. I asked them to turn wifi off on their phones and they suddenly have access. I then asked them to reboot their routers and that fixed the issue for their PCs.
What would the ISPs have pushed to the routers that is causing this issue?
Then it’s an issue between their ISP and your server. Whether the problem is with your server’s networking or their ISPs is complicated to discern and unless you can convince whoever’s network is broken to change something there is literally nothing you can do other than move your server to a different provider or network.