'Could not obtain source: [object Object]' after Appium launches the app

I am evaluating Appium for my WPF app on Windows 10.

I am using the following settings to use the Inspector. When I click ‘Start Session’ button (File -> New Session Window and either ‘Desired Capabilities’ or ‘Saved Capabilities’) using the settings below, the app is launched and I see the message: ‘Gathering initial app source’, followed by 'Could not obtain source: [object Object]

“platformName”: “Windows”,
“app”: “pathtotheapp”,
“deviceName”: “WindowsPC”

After the app is launched, I am able to search the items by the elements that I know how to identify (for instance, user name field by its ID), but am unable to use the feature of the Inspector that I like to use, which is to locate the elements (i.e to find out the properties of the elements/controls as identified by Appium).

Delete the app if its already installed on the device and let appium session install the app! This will show AppSource on inspector