Artwork not showing

[bibates]

Hi 

I have had a NW-ZX300 for a few years. I have been transferring files as AAC without any problems. This week i decided to copy a few albums as PCM but the artwork wont show. I have tried deleting and copying artwork from a different file. No joy. Any help greatly appreciated 

[bibates]

Reckon the problem is that i import from cd using wav. 

If i set to FLAC it copies the artwork so that might be the solution.