Unable to use PURCHASED music in iMovie, continuing problem.

The last 2hrs has been nothing but a headache and Apple Support hasn't been able to help me either so I hope one of you can.

I am a Apple Music subscriber and while I know you can't use that music for iMovie because of DMR protection so I bought the song I was wanting to use (Pontoon by Little Big Town) for a family collage I'm putting together. I spent the $1.29 on the song, re loaded up iMovie, go to audio, sure thing there is the song I want to use! So I try and drag it to the audio bar at the bottom of my screen and it is grey'd out.

Got on the phone with apple support and they tell my to click on the song in my music library-- click file-- and convert file to CAA. THAT doesn't work either. I get error 50.

So WTH honestly want to get away from apple all together as a downloading service for these projects if it avoids these headaches. If there is another way to download name music and usable in iMovie Im looking for suggestions.