Q: When I open iTunes on my Macbook air the artwork to many albums has disappeared and when I open them, all the tracks have either an exclamation point in a circle or a grey lightening cloud. Some albums have disappeared off my phone too?

Hello miadler,

I understand that you are having an issue with your iTunes library showing an exclamation mark and one that shows a cloud symbol with a lightning bolt in it. Let's go over what the symbols are and what you can do about it. 

The exclamation mark symbol is letting you know that the music is not in the same location as it was previously. To fix this, you will need to move the music back to that location. If you don't know that location, you can get information by right clicking on the song and click on Get Info. Take a look at the first link for more details.    

If your music is missing from iTunes
https://support.apple.com/en-us/HT203167

On to the cloud symbol with the lightning bolt in it, that refers to being disconnected from Apple Music. Take a look at the next article that goes into details about this specifically. If the songs is unavailable, then that may also reflect on your iPhone as well. 

About iCloud Music Library icons and status
https://support.apple.com/en-us/HT203564​

Take care