exported xlsx files won't open with office 2016. Any ideas
export to excel and the file actually opens or works.
We experienced similar problem on windows 10 v.1607 (Anniversary Update), but the problem gone with windows 10 v.1703 (Creators Update). Seems like there was a bug in v.1607 and it's fixed in 1703. If you use v.1607 we strongly recommend you to apply Creators update.
You are talking about windows 10 app, aren't you? If so tell us your windows version and build number.