Steps to reproduce:
The important information here is the version of the Microsoft.Toolkit.Uwp.Notifications: 220.127.116.11
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 18.104.22.168 even though in the installation folder we distribute the updated version 22.214.171.124:
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 126.96.36.199.