I think it could be a computer memory issue,
My Toshiba laptop is almost six years old, a $300 budget thing. And it can do basic writing, browsing, and YouTube videos. Any kind of HD streaming on Spectrum TV.net or video content with Flashplayer, it just stutters on Firefox and doesn't even play on Microsoft Edge Chromium. This above information is the same with the new HBO Max service.
In contrast, my Dell desktop has 8GB RAM, streams the above sites like a dream and works great! It seems that you need at least 8GB of RAM and a decent graphics card to be able to do the HD type of streaming required at Spectrum TV.net and the other above sites that I mentioned where my cheap laptop has always had issues for years.
Jn my case, both computers run Windows 10 version 1909 and are up-to-date The laptop update to Windows 10, was an upgrade from Windows 8.1. Back when it had Windows 8,1, it had the same streaming problems. A hardware related and memory related incident for the laptop, that is preventing the viewing of streaming data on HD video sites.
Satch