scheduling a function containing the playsound command plays no sound

Create a function that contains a playsound command, such as;

playsound minecraft:entity.experience_orb.pickup master @a ~ ~ ~

this will play the sound of an XP orb being picked up, on the master slider to every player.

When the function is ran using the /function command it plays as expected, but if the function is scheduled using /schedule the function triggers but the sound fails to play.