Must have been user error. Seems to work properly now.
Another question, if I may. In Popup Settings, when I choose Link to URL for the Click Action, the only choice displayed is a field for Link Target. I expect to put something like _self here, but should there be a field to enter a URL. I know I can specify a link URL per item, but a default action for all of them, like this seems to be, would be great.
Thanks again.