That looks ok and i am assuming cover.jpg was active in the artwork settings at the time you imported the music files.
The only other thing i can think of is to confirm the cover artwork file actually has a .jpg extension.
You might need to change your windows explorer view settings to confirm that
sorry I am a dinosaur when it comes to technology...so could you please expand on:
1. where do I find cover artwork file?
2. Windows explorer view setting?
I must also admit that I use MusicBee on my office computer (PC) which has Windows 10 and the music is located on an external Harddrive connected to PC via USB - all the pictures work fine and the music in external HDD is an exact copy of the folders on my NAS.......
Perhaps it is Windows 7 that is making the artwork disappear?