Garageband loops can't be heard and downloading more audio doesn't help

How come when in GarageBand, and I drag a loop into the timeline, it says it needs to download more audio but when it does the clip still can't be heard?

Also, I deleted the index from the Apple Loops Index hoping to force a re-index to fix the above problem, but despite emptying trash and restarting, no new index was created.

What to do?

Regards

Royks