I'm having this issue on a Dell XPS 15 4K 2-in-1. This is not an internet issue, it is my pc.
I also cant restart my pc when it happens I believe because my pc cant end the process either so I have to restart my pc by holding the power button. Also, any time this issue happens, if i try to close the launcher, it still shows up in my processes on task manager, and if i try to end the process it says the operation could not be performed. I've tried so many solutions from the internet and sought out tech support but I never found something that worked. done clean boots, disabled my anti virus and firewall, ran it as administrator, cleared my cache, updated all of my drivers, and reformatted my drives. It is not my internet provider, all my other pc's and devices download things just fine. I will get about 1 - 2 GB into the download and then my download speed goes to 0 B/s and never goes up. So basically anytime I'm downloading games. It happens on Steam, Origin, Riot Games Launcher, and the Epic Games Launcher. I've been having this problem for about 3 weeks.