Since Xp 1.13, in XP you have two ways to update XP. Either by downloading the last available package from your user account, or by updating all systems remotely. Unfortunately for the Mac OS , there is a problem with the Xp 1.13 version that requires you to correct the permissions rights to the application before upgrading. Please be sure to follow this video that explain how to correct it before updating this way.
If you have problems, the workaround is simply to download a whole package from your account.
Don't forget to always use the right devices package corresponding to the right version of the application.
Windows version, there shouldn't be such a problem, but let us know. As we said, it's a new feature which is in general implemented for larger project, but we find that's a pretty cool one that we would like to see properly working in the future.
Don't hesitate to write us if you have any problems