OK, I'm not entirely sure why it's giving the 503 or the "unable to service your request due to maintenance downtime or capacity problems". I tested here, and having a CDD watching a calc element works. But it's definitely the "watching a calc" which is the problem on your site - if I change "weeks_pregnant" to be a simple field, it works.
However ... even if it did work with your calc, there's other problems. You have lots of calcs which use other calcs in their code, as placeholders. You really can't do that in Fabrik, as there's no guarrantee as to what order the calc will be executed. So if calc1 relies on calc2, but calc1 runs before calc2 ... the result will be wrong.
Also ... calcs only update the database when you save the form. So in your case, you create and save the form, all the calcs run (and for the sake of argument, lets say by chance they all execute in the right order to your trimester, weeks_pregnant, days_pregnant etc values are correct), and the data is saved, and the "weeks_pregnant" is (say) 5.
Now wait a week and load the list. As you have "calc on save only" set to No, your calcs will be re-calculated on the fly as the list renders, and the values will appear in the rendered list correct, weeks 6. BUT ... in the database itself, the weeks_pregnant will still be 5, because you haven't edited/saved the form. Which is going to mess up the CDD, which on page load is working from the value in the table, not the re-calculated value that gets rendered.
So ... you kind of need to re-think the way this form works.
-- hugh
