Yeah, since level 1 support is mostly following a script it's difficult to communicate that this is an app-wide issue and not a user-specific issue. You just have to humor them until it gets to level two support. I sent them a screen recording of me reproducing the error and another one of me scrolling through 3 pages of the most recent one-star reviews on the Microsoft store complaining about HTTP error. If you want to do the same, I highly recommend recordit.co which is free for recordings up to 5 minutes. Note that the recordings are publicly accessible to anyone that has the link you give out, but you can crop just the part of the screen you want to record before you start and can delete recordings.
Here's my recording of just the first 3 pages of bad reviews: http://recordit.co/AtpoyhxheD