I already paid. Why am I asked to subscribe again?

A subscription belongs to the PlayBoox account that paid for it. Check that the app is signed in with the same email or phone you used to pay.

Close the app completely and open it again, so it reads your subscription afresh.

If it still asks you to subscribe, raise a ticket from any help page (the button at the top right) with the transaction ID from your receipt, and we will look it up.