Plex will sometimes be unreachable on wired connection with internet working. Why?

If you have to restart the machine itself, that’s where the root cause is.
Remember, the OS is what manages the adapters. If it’s not recovering from a flaky connector or, worse, the adapter chip itself is failing (can happen), this is how it will manifest. Transistors do fail. They don’t often but do. The most common transistor failure is in our modems. It must ‘push’ all that signal (power) up the wire to our ISP.

Thank you SO MUCH! I can’t believe it was the cable all along. I’ve replaced it and ever since I’ve never had the connection go out. My only issue now is that sometimes when I upload, whatever I’m watching crashes, which never used to happen before. I’m guessing it may have something to do with the port I’m using or my router. It’s one that’s supplied by Optimum. It’s their brand new model, but it has limited customization options.

I may play around with the ports later. Thanks again!