Album artwork Windows 8. iTunes 12.1.2.27

I am unable to upload an image to an album.

Most of the time I use the "Get Album Artwork option" which works if the album is available in the iTunes Store.

Otherwise, I try to right click on album>Get Info>Artwork>Add Artwork but it will not work.

I use a program to convert from FLAC to Wav which preserves the ID3 tags as well as the artwork.