iTunes Artwork not modifiable
I recently bought a new Macbook pro. I have all my music saved on an external Hard Drive and it took 60 hours to transfer 25,000 songs to iTunes. I though this was very slow but it may be because the files within the music folder were not organised well enough for iTunes so it took longer to transfer the data. When it eventually finished everything seemed ok except there was a lot of artwork missing. On my previous laptop I had to manually drag and drop the missing artwork from the internet so i thought it would be a simple case of doing that again.
Unfortunately iTunes won't let me do this as the square on the bottom left of the screen where the artwork would show says "Artwork not modifiable" or something similar. I am not a whizz on computers so I am a bit stuck. I went to the music folder on the external hard drive and rightclicked to click on "Get Info" and it says that it is read only. I need to know:
WIll this cause problems in the future when I buy songs through iTunes on my iPhone etc. These would then normally be added to the music files on the external hard drive when I attach it and open up iTunes?
Why has the hard drive changed to read only?
How can I fix this?
😕
MacBook Pro (Retina, 13-inch, Late 2012)