Recreation steps:1) Navigate to powerpoint file in Teams2) Select Edit in Teams3) Select presentation mode at bottom left corner4) Receive non-English error message: "You'll need a new app to open this about"
Thanks for bringing this to our attention.
I have managed to replicate this. Reader view works fine by slide show/presenter view throws that message when in edit mode in Teams. Of course, works fine in PowerPoint.
Recommendation is to
1.) Raise as a ticket to Microsoft via the 365 admin portal
2.) Raise as a bug here on Teams Uservoice: https://microsoftteams.uservoice.com/forums/555103-public (add item with BUG: prefix)
I can't find any other source that confirms it is a bug, but I can't imagine that it would be by design.
Hope that answers your question - and would be great if you could confirm the response from Microsoft after raising.