Copied files to NAS, now cannot add or edit permissions

I admit I'm pretty confused about the the share setup screens and what it was asking me to set up in Read/Write Access and Advanced>Share owner, but since I was able to copy files over to the new shares, I assumed I was doing something right anway.

But, the files didn't bring all of their security info (I used robocopy). Also, CREATOR OWNER has no rights, and I even though I am a domain admin to the AD this is connected to, I cannot change or add any of the file permissions or take ownership of the files. I get and "Access Denied" error. I can't even change the "share access settings" anymore. Just tells me that my AD groups were removed because they are "invalid" (like administrator and Domain Admin)

All the very scant documentation I have been able to find on using the Readynas with windows just says "Right Click and add your users" like there's nothing more too it, but this obviously can't be the case, given the unusual and unexplained behavior I've been seeing with my file permissions.

Can someone point me to some additional instruction on this? I have a non-trivial set of access rules but I can't even figure out how get it to let me set permissions on my files and folders!