I already have a Vélib' subscription on my Navigo pass, can I use it to buy Vélib' offers on the Île-de-France Mobilités app?

If you already have a valid Vélib' pass or pass on your Navigo pass, you will not be able to use the same Navigo pass to buy another one: 1 Navigo pass = 1 Vélib' pass.
However, you can still buy Vélib' offers on the Île-de-France Mobilités app, by choosing the codes as the unlock method.