Move Adobe PDF Services API trial account to a suscription account

I've an AWS account with Adobe PDF Services API subscription. In Adobe Developer, I've one project, that is a trial account with 1000 transactions, and I want to change it to a suscription account (payment by use, without limits), but if I try to use the option of "Create new credentials", it says that "You already have a credential".

How can I create these new credentials to a suscription account? Do I have to delete the project and create a new one, or is there a way to change it?