Make sure your Song is located in the Workspace in your Explorer Window and NOT inside of a Part. Drag and Drop the Song onto your Workspace at the top to fix this in your Explorer Window.
Delete any Extra Songs in your Explorer Window. You should only have 1.
Select your Song.
In the View tab click the Properties button on the left to open your Properties Window.
In the Properties Window find the Data section.
Scroll down and Check the box for Looped and Playing. Make sure these are checked, otherwise you won’t hear your song during gameplay.
Troubleshooting: If you can’t hear the Song, try going into Play Testing and find your Settings. The settings is located in the top left corner of the Play Testing window it looks like a (Grey Roblox Square). From here, turn the Volume Up and try to Preview the song again.