Just found a glitch with the ES file explorer within Nvidia Shield so when you try to use the Remote Manager it tells you to input this ftp://192.168.49.1:3721/ or something like this if you notice the 49.1 part is not even in your network range.
What i did you just to go ahead and type in the normal IP address of the Nvidia Sheild some thing like this ftp://192.168.1.15:3721 it almost worked i got and error about passive mode so in my ftp client i just set it to Active (Port) and guess what it worked!!!
I can now access all the files in my shield from my computer.
Hope this helps you out