Try this to force The Android media scanner to rescan all media.
This will only work if it rescan sd card media. which it may or may not depending on alignment of stars:
- go into Android Settings > Apps (or equivalent with app list), then 3
dot menu > Show system apps
- in the list, locate the 'Media Storage' app and tap on it
- go into the 'Storage' section then tap button 'Clear data'
- reboot your device. Android will rescan all your media. This can take
=> check if the album art is now visible