Relevant code: https://github.com/mozilla/webpay/blob/master/lib/solitude/api.py#L266-L279 In webpay, when starting a transaction to purchase an app, it will attempt to look up a generic product using the pair of a provider specific seller_uuid and the app's external_id. No such product will be found because a generic product with that pair is not created by Zamboni, only a generic product with a dummy seller_uuid which is not bound to any seller account and the app's external_id. We need to either a) Create generic products in solitude with all provider specific seller_uuids and the app's external_id when accounts are set up in zamboni here: https://github.com/mozilla/zamboni/blob/master/mkt/developers/providers.py#L383-L409 or b) Update the 'create_product' method in webpay to function correctly in this situation and lazily create the new generic product here: https://github.com/mozilla/webpay/blob/master/lib/solitude/api.py#L300-L334 Presently this scenario will fail on this step: https://github.com/mozilla/webpay/blob/master/lib/solitude/api.py#L327-L332 after having successfully created the generic product, so it will fail the first time someone attempts to buy an app on a given pay provider, and then succeed the second time, making it something of a heisenbug.