Some album covers don't appear on lists - iTunes 12

Hello,

I installed an SSD on my iMac (27 inch, mid 2010) and copied and pasted the iTunes Library.itl from the previous HDD to the SSD today. And, in the preference window of iTunes 12, I relocated iTunes Media folder to the one on the previous HDD.

But SOME of the album covers don't appear on lists even though they all have their album cover arts correctly.

See the screenshots below:

How can I load all the album covers successfully? Please help.