Albums does not always show up as expected


I have a library containing about 10000 FLAC files and 6000 MP3 files. These music files are organized in one folder per artist. Each file in the artist folder have an embedded Album picture with a size of 800 x 800px. I do not have Album.jpg or Folder.jpg. with my files but every file is tagged with the Album name. I have downloaded and provided each file with the correct album image using dbPoweramps ID-Tagging or I have used that same feature to load my own created album image.
The Album art is visible if I play a file in Windows Music Player alternatively AIMP. But, when I play the same files through my Streamer using Volumio many files do not show my embedded Album Art. I have mostly used dbPoweramp tor RIP. The Album Art shows up when I check the Edit ID-Tag by right clicking on the file. It also shows up under Properties when file is selected.

Just wonder what could be wrong here? And, is it absolutely necessary to create a Folder.jpg in order for the Album to show up in Volumio? In that case I have many many hours of work to do :frowning: