I'm having the same problems as the OP and in the video. I can connect to Helix Stadium Windows App via WiFi and it won't download
It says WiFi/Ethernet update not available, connect via USB.
Every time I've tried to connect the via USB the Helix Stadium app crashes in windows every time.
I also tried the Line6 Central software and Maintenance mode reset as suggested here, which didn't work for me either.
[Update: Using a iOS on a macbook allowed me to connect the Helix app to the Stadium and update to 1.2 via USB]
Thanks,
Gabe