To update the chat client in a network under the Active Directory management you only need to replace the package file.
1.Download an MSI package of a new version of MyChat on the official website.
2.Go to Group Policy Editor, choose GP "MyChat".
3.Enter the "User configuration" — "Policy" — "Software settings" — "Software installation".
4.Choose the installed setup file of the previous version and delete it.
In the context menu choose "All tasks" — "Delete":
In the dialogue window select "Complete deleting..." to delete programs from user computers before installing a new version.
5.Now you need repeat a couple of operations from initial chat installation in AD. Add a new package and make it as "assigned".
A new chat version will be installed after applying Group Policy.