A Single Login Page Keeps Timing Out

Suddenly we are timed out at the login page of our investment advisor. A major company where we can access the main page, (and everything else on the internet) but the login times out on all devices, and all browsers.

Outside the home and on other wifi there's no problem. Mobile data access is also fine. Even tried a VPN and that works. Attempts at solving this issue over the phone failed, but before moving to a higher level of escalation I was told Xfinity has to send someone out to check a "signal issue" that appears in their system. As far as I can tell I'm not having any signal issues and I'm waiting for the tech to arrive. I'm hoping he can focus on solving my problem without creating multiple others. I'm just trying to figure out who is blocking my IP address and why. The company itself says it is not them. It's just strange that this website is the only one having this issue. One that we have had zero problems with for years.

I will follow up after the appointment.