@noob_dev
we have seen you are using Windows - Legacy
So when checking the details from the docu:
we can refer to the details:

- close the xaml
- Take a backup from your XAML
- open XAML in a texteditor (e.g. notepad++)
- ensure following line or add it:
- reopen the XAML in UiPath
- import namespace:

feel free also to import:
After these steps we can see:

