NX Rerouting connections fail in some environments

Why does rerouting connections fail in some environments?

If the assembly load options for reference sets have the below settings.

 Reference Sets    : Use Model, As Saved, Entire Part, Empty

Auto route may not work.

The above setting forces the components to load "Model" reference set

Model reference sets do not have routing ports.

As ports are essential for "Auto route", It fails.

It is necessary to load a reference set that contains ports (or Entire part reference set)  for auto route to work