I have a phone with an unlimited data plan that I use for my internet as the wifi that comes with my apt is terrible and slow. The problem with that ARC launcher is, that it does not recognize me as being connected to the internet when I am tethered. I have been tethering for almost all my internet needs for years and this is the first time I've had this issue.
This wasn't a problem with neverwinter as it lets you launch the game without ARC because it has it's own launcher that you used to log in and update (double launchers.. wtf right?). That game runs fine tethered btw. My problem is with the Torchlight Frontiers Alpha as it requires the ARC launcher to log in.
I had to install that one with my shitty wifi and play as well. Due to the nature of my connection it makes the play experience unbearable most times.
You need to make your launcher recognize tethering as more and more people are using that to get their internet. Especially with the advent of 5g phones.