MP3s from iCloud Drive are greyed out, can't be imported

The latest version of GarageBand now allows you to import files from iCloud Drive, which I hoped would prevent me from having to go through iTunes to get MP3 files into it. It's almost there, but it still won't work. Here's what I've done:

I have an MP3 file on a USB thumb drive which I capture from our audio system at church.

I have a RAVPower device that allows me to access the USB thumb drive from my iPad and email the MP3 file to myself.

In Mail, I save the MP3 file to iCloud Drive.

In GarageBand, I use the "Import from iCloud Drive" option.

All of the above works (it's still way too many steps, however, if you're listening Apple...)

What doesn't work is the file shows up as grayed out in the Audio Files section, and I can't drag it onto a track in GarageBand.

Anyone know what would cause this? Is there some default behavior where iOS assumes MP3 files might be protected or something?

Thanks-

-tb