I've had that problem on Windows 10 builds 10130 through to the 10240 TH1 release with MS Edge. There have been several EDGE update patches since. The problem seemed to disappear with one of those patches.
During the same period, Google also denied access to
https://hangouts.google.com/ from all users connecting with MS Edge, be it through Windows 10 or any current Windows Phone 10 builds.
https://www.reddit.com/r/google/comments/3iexwy/google_locked_out_microsoft_edge_browser_users/Probably totally unrelated. But when I tested Hangouts on GooglePlus, using MS Edge, it rendered very poorly, and everything that was not supposed to scroll, scrolled. Fixed-location elements did not stay set in their fixed locations. Chrome and Firefox do not have this problem.
I couldnt tell you exactly what was done to fix Edge since 10240 RTM. But it may be related to a Windows 10 update patch since then.I dont have the problem right now. And I am able to login just fine to UBBCentral using MS Edge on Windows 10. But I am currently on Windows 10 build 10565 for my primary desktop. And Windows 10 with all the current update patches for my secondary desktops -- 32bit and 64bit on each of those.
Though, the login problem still persists using MS Edge on clean install of Windows Phone 10 build 10536.---
My results:
Windows 10 build 10240 TH1 RTM -- has login issues for me.
Windows 10 build 10240 TH1 RTM with all update patches installed -- works for me.
Windows 10 build 10565 -- works for me.
Windows Phone 10 build 10536 -- has login issues for me.
