We've noticed an issue when Skype for Business users try to add Skype users who use the Windows 10 native/UWP app. The invitation to connect never shows up in the app and SfB just gets stuck at "Pending." The users cannot chat or call. SfB to Skype users still using the classic desktop application works just fine, with the invitation usually arriving within a few minutes. (I have not tested accepting the invite in the classic app and then trying the Windows 10 app. This isn't a suitable workaround for hosting external Skype calls and interviews)
Has anyone seen this before? We've tried different accounts, different computers, reboots, and sign-outs. It's happened to a handful of users of both SfB and Skype, internal and external. We have no known reports of success with Sfb->Win10. I've tried to search online but haven't found the right keywords to indicate it's an issue in the Windows 10 app and not Skype in general.
