You may not be able to remove it depending how tight that set screw was.
If it marred the threads you're fucked. You'll have to send it back to them and buy a new tube.
I have a gen 1 Envy and that tube is on there but good. Tried a vice, all manner of wrench, heat, won't budge.
If I go to a cheater bar or large pipe wrench I'm just going to bend the chassis. Not worth it. So it's a fixed model at my house.
They can get it off for you if you're willing to ship it to them.