Cover art for mp3 missing in iOS Files app

Hello CraigMau,

Thanks for reaching out to Apple Support Communities. We see you have some questions about your cover art not showing, and we'd like to help. As we see you synced with the Apple Music app, we'd recommend trying to sync with Finder, and let us know if the issue remains: Use the Finder to sync your iPhone, iPad, or iPod with your computer - Apple Support

Sync or remove content using the Finder

1. Open a Finder window and connect your device to your computer using a USB cable. Learn what to do if you don't see your device listed in Finder.

2. After your device appears in the sidebar of the Finder window, click the device to select it.

3. If prompted, trust your device. You might be asked to update to the latest version of iOS or iPadOS.

4. Select the type of content that you want to sync or remove from the horizontal list. To turn syncing on for a content type, select the checkbox next to “Sync [content] onto [user’s] iPhone.” More syncing options will now be available.

5. Select the checkbox next to each item that you want to sync.

6. Click the Apply button in the lower-right corner of the window. If syncing doesn't start automatically, click the Sync button. You may also be prompted to authorize your computer to complete the sync.

Let us know if this helps.

Regards.

Understood CraigMau,

What we would recommend in this case is to contact Apple Support. They can help look into if this remains supported and what other functions may be at play here. Contact - How to Contact Us - Apple

Cheers!