I'm having the EXACT same problem! I just received my new Stadium XL yesterday and I've been messing with this thing non-stop. I can't even get it to connect via USB-C, and I've tried multiple USB cables and multiple PCs. I've tried all of the solutions I've found online with no results whatsoever. I just created a ticket with Line 6 support. I've never been so frustrated with a piece of new $2K+ gear!