Best practice for requiring an “access code” before user can use app

To put things into context, we have an app that lets users earn money by just learning.

Because of this, we have to be quite strict about which users are allowed to sign up as we obviously have limited funds and we only want “authorized” users to be able to use the app.

We’ve created an access code system and previously we’d ask how they heard about the app and then after they select an option we ask them to enter an access code. It looked like this:

enter image description here

The problem we had with this implementation was:

  • Users got confused and would sometimes drop off.
  • Users who didn’t have an access code got confused why they couldn’t access the app and left bad reviews.

So, now we’re redesigning the flow, and our idea is to just have 1 textarea where they can enter their access code:

enter image description here

With this new design we’re hoping that it’ll be a lot more clear, and for the users that select that they don’t have an access code we’re thinking about letting them use the app without being able to earn money.

I’m wondering if all you experienced UX designers have come across an implementation like this before.

Any tips or advice would be great. Thank you.