Pre-order Credits - Credit Not Applied To Acount In Test Run

I'm just getting my new offers set up, and tried using the Pre-Order credits. 

When I did my test checkout using my own customer account, no credit was applied to my account. 

Things I did which I think might have had an effect, but I'm not sure which specifically might have caused the problem/s. 

1. I added the Pre-Order credit to a collection. This was to enable additional options input (name and class). Could this have caused the problem?

2. I had the pre-order credit on one price list, and then changed the gallery to a different price list (aka the one with photo sales on it)

Those are the only things I can think of that might have had an effect.

Any assistance appreciated! Thanks!

I didn't intend for the pre-order credit to be used within a colleciton. That will currently not work. I intended it to be a product on it's own, not within a colleciton. So this will not work at this time.

Thanks Tim. I'll work out another way to do it. 

Unfortunately since it's pre-paid, we need to collect some information about what child the re-order is for, which we can do with additional information on the price list level, but that won't work if someone is purchasing multiples for siblings within one transaction :-( 

They can place separate pre-orders for each child.