A cover song is a song that you performed & recorded yourself, but the music was written by someone else. For example, when your band plays "Blackbird" (written by The Beatles).
To release a cover version (ie: A song you didn't write), you need the necessary permission from the rights holder(s) - that means the writer/s of the original song or their publisher/s - and this is usually done by obtaining a mechanical license.
In the U.S. you can purchase a mechanical license from The Harry Fox Agency or Easy Song Licensing.
If you release a cover song, make sure to enter 'Version' when asked if your release is a Cover Version, or remix when creating your release. Then please contact our Customer Support team with the required documentation. After you have provided this, only then will your release be sent to stores.