This error message occurs when there are multiple fields in the calculation and they are not all aggregated. In this formula, [Goal Tracking] is not aggregated. However, this can be fixed by simply adding an aggregation to it, similar to the following:
IF attr([Goals Tracking])=" Goal 1: leads to active" THEN STR(sum([today_status]) + " leads today" end
Hope this helps!
Thank you very much!!!