I am not sure how many of you had to re-os, power off multiple times, or restore. So, try these and hit 'like' and/or 'This solved my question' or 'This helped me', if it works as explained below.
What you do on the iTunes is what appears on iPhone. Artwork missing in iPhone is unlikely, if iTunes on PC has them. I am going to be very simple in writing, for everyone to understand as clear as possible. Follow the below steps -
1. Go to iTunes (On PC). Right Click and select 'Get Info'.
2. If any error message gets displayed there, try to play it once or locate that song manually, if you have recently changed the location.
3. Select 'Artwork' tab and ensure the artwork is still there.
4. (Here is the funny part) - Go to 'Info' tab (the tab between 'Summary' and 'Video')
5. Ensure for any particular song, the following values are always captured -
a) Name -
b) Artist -
c) Album - (Most of us tend to delete this album data, to avoid seeing duplicate of the name or artist)
Eg. On my iTunes (PC), a song is categorized -
a) Name - Bad Day (Ladies and Gents - I did not purposely select this song 😉)
b) Artist - Daniel Powter
c) Album - Bad Day
Try the above simple step and see if it works. If not, reply back to me and mention the exact error message. Can try to help.