Just updated Nexus 9. Now I can't open to get files when connected to PC. What can I do?

A

AC Question

When I connect my Nexus 9 to my PC via USB cable, I will see Nexus 9 as a connected device but I can't expand it anymore in Windows Explorer to see folders in the Nexus 9 to exchange files between PC and Nexus 9. It was fine until right before the last update today. What can I do to fix this?