Folder permissions have changed (are locked) after servicing our NAS

've run into an issue with my NAS and Mac not playing together nicely. and was hoping that one of you who is more tech-savvy than I am (it doesn't take much, honestly) might be able to point me in the right direction. Recently the Mac Finder app has been displaying little red circles with a dash inside and is telling me I don't have access to my files on the NAS. I've tried resetting the permissions as Apple support describes, but I still have the issue. I've reset security settings on the NAS. These came over to the NAS from a Windows 10 PC, but the permission thing is new. Any thoughts?