I can not download my application on PowerApps windows anymore. I tried on Surface Pro 4 and on PC and both do not work.
This message appears in both cases :
Can you try to create a new app in de https://web.powerapps.com site and try to download it to your machine?
If this is only happening for 1 app something might be wrong there.
You should take contact with Microsoft regarding your issue.
This can be done here: https://powerapps.microsoft.com/en-us/support/
Hope you get this fixed.
If/when it does get fixed let us know what the issue was.