Some songs on a local files album have album art, some aren't

[megadude1234]

Hey. So recently, I downloaded an album that wasn't on Spotify and imported it onto Spotify (via. Local Files). However, after importing it, I realized that the album art showed on the desktop, but it failed to show on my phone. After some fiddling around, I managed to get some (if not, most) of the songs to display the album art on my phone, but there are still some songs that are missing the album art, and it just so happens to be the songs that I added to my playlist. Is there any way I can fix this issue, and make it so all songs on my phone display the album art? It'd be appreciative.