Tags not appearing in Properties

Made tags of flac files using Mp3tag. Noticed that the tags do not appear in Properties (Properties>details>tags). Ran the files through mp3val which generated the error 'Unknown file format.'

Here is a copy of the metadata.
Metadata

D:\Audio\Classical\Bach\Bach_The Art of Fugue_Munchinger\08. Bach - Die Kunst der Fuge, BWV 1080 Contrapunctus VIII.flac

Name: D:\Audio\Classical\Bach\Bach_The Art of Fugue_Munchinger\08. Bach - Die Kunst der Fuge, BWV 1080 Contrapunctus VIII.flac

Size: 32.1 MB
Item type: FLAC File
Date modified: 21-Dec-16 10:22 AM
Date created: 21-Dec-16 10:19 AM
Date accessed: 21-Dec-16 10:19 AM
Attributes: A
Availability: Available offline
Perceived type: Audio
Owner: DESKTOP-I94GF2J\Stephen
Kind: Music
Contributing artists: Bach
Album: The Art of Fugue (Munchinger - Stuttgart)
Year: 2000
Genre: Classical
Rating: Unrated
Authors: Bach
Title: Die Kunst der Fuge, BWV 1080 {08} 8- Contrapunctus VIII
#: 8
Length: 00:06:09
Bit rate: ‎731kbps
Total size: 286 GB
Computer: DESKTOP-I94GF2J (this PC)
File extension: .flac
Filename: 08. Bach - Die Kunst der Fuge, BWV 1080 Contrapunctus VIII.flac
Space free: 198 GB
Shared: No
Folder name: Bach_The Art of Fugue_Munchinger
Folder path: D:\Music\Classical\Bach\Bach_The Art of Fugue_Munchinger
Folder: Bach_The Art of Fugue_Munchinger (D:\Music\Classical\Bach)
Path: D:\Music\Classical\Bach\Bach_The Art of Fugue_Munchinger\08. Bach - Die Kunst der Fuge, BWV 1080 Contrapunctus VIII.flac
Type: FLAC File
Link status: Unresolved
Date released: 2000
Album artist: Bach
Space used: ‎30%
Shared with: Homegroup
Sharing status: Shared

MP3val evaluates only mp3s, no flacs.

For the tag-display-problem see this thread:
/t/17170/1

There seems to be a length problem for tag fields. And classical music has very often such long titles.