RE: YouTube states that video about charity is not suitable for advertisers

It can be fixed :)

There are options to resolve the issue - the rights owner can remove the claim only for your video.

You can contact AdRev support and let them know that you have the owner’s permission (or license) to use the music.

You could also file a dispute on YouTube. That is the slowest way.

Here is a good post on how to resolve issues like yours :
https://www.miksmusic.com/resolve-adrev-third-party-copyright-claim-youtube-video/

There is just one thing.. sometimes the artist doesn't have the copyright to their works... it goes to the producers, recording studio etc. Then his/her permission may not be enough.

If the artist has the rights, the studio is another entity and is monetizing the artist's work, he/she could file a claim against them :)

Here is a good place to read more about music copyright:
http://tubularinsights.com/copyrighted-music-in-video/