Cannot create a sideload project in VS2019

Question

Here is the problem. When I select 'Create app package' in the Publish submenu of the Project menu of VS 2019, I am given two choices in the window that appears. They are 'Microsoft Store under new app name' and 'Sideload'. I want to create a sideload app package for testing purposes. For some reason, I cannot select (turn the radio button on) for the 'Sideload' option. Anyone know how to allow me to create my sideload app package. Thanks.