Transferring Files From Mac Hard Drive To WD MyCloud Using Finder

Hello, I am new to this community, and would like to let you know about a problem I am having with my WD MyCloud.  Until recently I have been able to transfer files from my Mac Hard Drive to WD MyCloud using finder,  but for some unknown reason I am now prevented from doing this.  Each time I try, I get this message pop up, “Some files can’t be processed, either because you don’t have permission to modify them, or because they are on a locked volume”.  It also happens when I try to transfer files from my external hard drives to WD MyCloud.  But, if I use the MyCloud App. there is no problem they just flow across without incident.  Is there an answer to this problem?  I prefer using Finder because it gives more detail of the files I am transferring.  Many thanks  Jim

When you use finder to transfer the files, you must be connected to the NAS. Are you connected with a user that has the right read/write access to the shares?