RS700 Router - Cannot Access Sub-Folders on USB-Attached External Hard Drive

I purchased the Netgear RS700 router this weekend, which is an upgrade from my Netgear Nighthawk RAX120.  I had an external hard drive attached to the RAX120 via USB, where I could access all files (parent and sub-folders) over WiFi.

With the change to the RS700, I am only able to access the parent folders.  I cannot access any sub-folders, which creates a problem.  I can't access any files - office docs, videos, music, etc.

Others have stated it's probably a configuration issue.  I just don't know what configs I should be looking at to correct the problem.

Any suggestions to help would be very much appreciated.

Thanks!