I'm trying to debug a function in some app script for my Google spreadsheet. When I choose my function (called Calc) from the drop down and hit the Bug icon to step through it, all I get is a message at the top of the IDE saying "Preparing for execution...". Is there something else I'm supposed to do?

BTW - I thought of posting this on the google forums but I noticed that all the support team for app script seem to weigh in here. Hope this is the right place!
Line 13 is wrong. See the order in for loop. Will never stop as is.