Innovalog JIRA Misc Custom Fields - Can't get customdatefields to compute in Calculated Number Field

[C]

Hello, I am having some trouble with Innovalog JIRA Misc Custom Fields.

So the following syntax works. I'm able to get the duedate - created in days, which is exactly what I intended. 

<!-- @@Formula: issue.get("duedate")==null ? null : (issue.get("duedate").getTime() - issue.get("created").getTime()) / 1000 / 3600 / 24 -->

However, once I changed it to a custom date field, it won't work. 

<!-- @@Formula: issue.get("customfield_11044")==null ? null : (issue.get("customfield_11044").getTime() - issue.get("created").getTime()) / 1000 / 3600 / 24 -->

The field doesn't work whether it's a DATE PICKER or a DATE TIME PICKER. 

This is JIRA 7.2.7

Any ideas what I am doing wrong?