Missing album artwork on iPhone on iTunes Match

When I added a new album to my itunes in windows 2 days ago, i opened my iphone to make sure the album appeared as i have itunes match. the album appeared but the artwork for that album and all my other albums disappeared.

to try and fix it I swtiched off "icloud music library" in my iphone settings which cleared all the ablums and then switched it back on. This normally fixes these types of issues but it did not work. 2 days later none of my album artwork has appeared.

My software on both iphone and windows is up to date.

thanks