Steps to reproduce:
The important information here is the version of the Microsoft.Toolkit.Uwp.Notifications: 126.96.36.199
After the upgrade process is successfully completed, you can see that the Toolbox version is successfully updated as well as the Telerik references in the project:
However, the version of the Microsoft.Toolkit.Uwp.Notifications still remains 188.8.131.52 even though in the installation folder we distribute the updated version 184.108.40.206:
Then, if you try to build the project, you will see the following error message:
Workaround: Remove the existing Microsoft.Toolkit.Uwp.Notifications assembly and add it anew using the references from the installation folder: C:\Program Files (x86)\Progress\Telerik UI for WinForms R2 2021\Bin40 It is expected to be the correct version 220.127.116.11.