Built-in field hasn't been mapped

The general field mapping on the host platform (e.g., the Jira instance on which you have installed BigPicture) hasn't been done for a particular field.

The mapping of tasks in a particular Box is irrelevant. The check is performed just for the general mapping of the primary instance. 

Example

BigPicture is installed on the "nostromo2" Jira instance. The host platform mapping is:

Open

The general mapping is on the left:

Open

To avoid the error when sorting by "End date" or "Start date," the following fields have to be mapped:

Built-in fields

The mapping has to be done if you want to sort tasks using the built-in field.