Starting from the version 13.1.0 of the iOS and Android app, you can easily add a free transaction to a specific device UUID (Don't you know how to find it? Please see here).
They can be used if you want, for example, to give access to your colleagues or to some customers in any particular cases.
Giving a free transaction, you will unlock one issue or all the issues included in a subscription period to a certain device. It means that the issues will change their status from "Buy" to "Download".
Go to your Dashboard, Features, Purchase manager, Free Transactions.
1) Enter a device UUID
2) check if there are any transactions
3) If you want you can add one (more) transaction just selecting the issue name or the subscription name.
PLEASE NOTE: Free transactions will be irrevocable. Free subscriptions are not auto-renewable.