It often happens to me that when I download tags from one of the services offered, this message appears
Please count the number of characters from D:\ until and including .flac.
If these are more then 255 characters, you reach the limit of max. path length in Windows as operating system.
I've counted the characters for you and it's below the mentioned limit.
Are the files maybe locked by another program? Can you edit the file if you select and just save via Ctrl+S?
Ok I'll try with CTRL+S