Wisej Ext ClientFileSystem - Error when calling methods

I am trying to use the Wisej.Ext.ClientFileSystem.ClientFileSystem.xxx methods and I get an error when I am using it at work:

A simple button on a form:

using Wisej.Ext.ClientFileSystem;

private async void button1_Click(object sender, EventArgs e)

{

Directory dir = await ClientFileSystem.ShowDirectoryPickerAsync(): –> This thows exception: System.ApplicationException: ‘window.showDirectoryPicker is not a function’

// Same error for below as well

var file = await ClientFileSystem.ShowSaveFilePickerAsync(true, filter, fileName); // filter = “json”; fileName = “NewFile.json”

}

Any thoughts?

Thanks!