RMStore author here.
When I make a call to purchase with the product ID I get an 'invalid product ID error'. Do my IAP items have to pass review BEFORE I can test them?
No.
I did some more testing. Even though I get invalid product ID when I try to make a purchase I am able to get the details of the products fine with the same product ID's.
Before purchasing products you need to request their details. If you fail to do so, RMStore will log "unknown product id" in DEBUG.
It might help to post the exact error message.