Silverlight based desktop application Select Item activity not working

I am automating a SIlverlight based desktop application. This has lots of combo boxes. However, the Select Item activity does not work on any combo box. I get the below error. Could someone please help?
I have installed Silverlight extension for UiPath.

Select Item ‘combo box’: Error HRESULT E_FAIL has been returned from a call to a COM component.