allegro:can not select unplaced component

I have a PCB file(.brd) and Schematic(.pdf) from our supplier. Now,I draw the Schematic in Orcad,the footprint of the part is from PCB file. Now,something happend. what i did is as follows.

1. I export the package from pcb file.

2. Draw the Schematic in Orcad.the footprint of the part is from pcb file

3.Create netlist in Orcad.

4. open the pcb file(.brd) in allegro pcb editor

5. inport the netlist.

 Now,after inporting the netlist of the Schematic, I find all components can not be placed. I want to know what is the reason, How I solve it. Thank you