"Preview could not be loaded" explanation



I'm having trouble getting one of my beast mode calculations to work, but domo provides no explanation as to why its not working.  Currently i've generated a simple table card about direct mail advertising, and on the table i have simple metrics such as title, costs, quantity, etc. 

When i try to generate a "Response Percent" (Total Responses/Total Sent), and its a simple query that was validated in Beat Mode, but when i try to include the column on my card, it reads "Preview could not be loaded, please try again"

Can anyone tell me why?

I've attached images of my Query, and my table before and after i added the column.

Thanks in advance for all your help!