Thank you Abhilash!
We updated the formula and set the parameters to Optional. The report is now working as expected.
A follow up question to you and Venkateswaran; If the report was working as expected to begin with what would make the report stop working? Our DBA confirmed that nothing changed on our database and to the best of my knowledge an infrastructure change (like installing a microsoft patch or updating anti virus software) shouldn't impact a report. Have either of you come across anything like this before?