How to go about licensing music for social media.

So I usually use epidemic sound for most of my videos, I have the business subscription which allows for influencer campaigns.

Recently I shot an influencer campaign for a medical company and used music from ES but when I submitted the video they asked for a license file for the music so they can clear it. I explained how epidemic sound works with safe listing and all that but they opted for me delivering the video without music rather because the system won't allow them to clear the video without a license.

So my question is which platform can I use that provides downloadable licenses when I download music? ES has the option to purchase single tracks when you log out but I don't know if it comes with a downloadable license?