Same here. The VPN button won't connect most of the time. When it does, I get the same "The webpage at http://xxx might be temporarily down or it may have moved permanently to a new web address" when I try to load any web page.

Perhaps using the developer version is kind of like being part of the Windows Insider Program...

I have the reverse problem. I can open any site with the regular browser but if I'm in a private window with VPN enabled, while opening any site I get: "The webpage at http://xxx might be temporarily down or it may have moved permanently to a new web address", same as you had.