I added a dynamic grid section from a library, but it doesn't contain any items

Check to make sure that the dynamic grid section's source object is the same in the study as it is in the library. For example, if the library dynamic grid contains item1 on section1 in form1 and visit, you must include that item in the same path. If your study contains item1 on section2 in form1 and visit1, the item is removed from the library dynamic grid when you add it to the study.

As a best practice, if you want to add a dynamic grid section from a library to a study, identify the visits, forms, and sections that its items are on, and add those objects in the correct path before you add the dynamic grid section.