Azure Files Currently does not have “Take Ownership” permission on the file share using Domain Auth So if robocopy requires setting the owner, it will fail with access denied.

“ERROR 5 (0x00000005) Copying NTFS to Destination Directory Access is Denied”.

Way around this is to mount the file share to a drive letter using storage account and key which uses a localuser which can be found per below

Make sure you run powershell as Admin , you will then also need to run cmd as Admin to be able to see the new drive share