When adding recipient criteria to a communication there are two ways to select multiple venues, leagues, seasons or teams.
The first way is simply to select multiple items by holding down the "Ctrl" key and clicking on each of the items you want to send to before clicking "Add" to add the criteria.
The second way is to add the items one at a time. When adding one at a time you should make sure that "Or" is selected in the first drop down box for the second, third and subsequent items. Otherwise Spawtz will try to send to all the users who exist in the first item AND the second item AND the third item etc etc. Invariably this comes to a sum total of zero users.