When opening a PDB file containing multiple models, as with a NMR structural ensemble, it’s read in as conformations of a single molecule. In the Data table, there will be a Conformation tab.

In DS these conformations are treated as trajectory conformations, only one conformation can be active at a time.

To see all the models at the same time, one can use the menu command Scripts > Structure Editing > Conformations to Molecules. This script will convert the conformations to multiple molecules displaying all in the active window.