Android : OpenIAB - How to get prices from inventory?

I'm using OpenIAB library to manage InApp purchases on Androrid.

I'm trying to get dynamically the price set on Google Play of each item that you can purchase but inventory.mSkuMap and inventory.getSkuDetails("SKU"); returns NULL.

I uploaded APK to Alpha channel yesterday, so I theoretically I shouldn't have this problem

I noticed that mSkuMap and getSkuDetails() retrieve data for items already purchased, so I'm confused because I thought that I retrieve all items with that and I should use getAllPurchases()or getPurchase("SKU") so, I'm wrong?

How can I retrieve purchasable items for my app?

Thank you.