Received mp3 files from an one drive link, but they are grayed out in Garageband import.

A band mate emailed me some mp3 audio of our practice session. He emailed them as a one drive link rather than an attachment. The link opens and plays the audio in Safari on my iPad. I told Safari to download. Download completed. Then I opened a new project on GarageBand on my ipad, set the section length to automatic, hit the loops and files incon, told GB to look in the downloads folder, the mp3 files were there, but they remain grayed out, unable to import. What is the problem here? I’ve used mp3 files in GB many times before. I noticed on these file that mp3 extension is capitalized. How can that make a difference?