OAuth credentials not linked as paid subscription after migration

We have a paid PDF Service API license subscribed via AWS Marketplace and been using Node SDK and JWT credentials to make API calls. This is the original code before migration:

const credentials =
  PDFServicesSdk.Credentials.serviceAccountCredentialsBuilder()
    .withClientId(JWT_CLIENT_ID)
    .withClientSecret(JWT_CLIENT_SECRET)
    .withOrganizationId(ORG ID)
    .withAccountId(ACCOUNT_ID)
    .withPrivateKey(PRIVATE_KEY)
    .build();

Using the servicePrincipalCredentialsBuilder() is the "new" way based from the sample code provided so we used this together with the OAuth Server-to-Server credentials and our code now looks like this:

// NEW_CLIENT_ID and NEW_CLIENT_SECRET came from the new OAuth Server-to-Server Credentials
 const credentials =
    PDFServicesSdk.Credentials.servicePrincipalCredentialsBuilder()
      .withClientId(NEW_CLIENT_ID)
      .withClientSecret(NEW_CLIENT_SECRET)

However, after a few days we started to receive this error "Either quota for this operation is not available or Free Tier quota is exhausted. Please visit (www.adobe.com/go/pdftoolsapi_home) to start using Free Tier quota or (www.adobe.com/go/pdftoolsapi_err_quota) to upgrade to paid credentials." which appears that the OAUTH credentials is linked as a Free Tier and was not associated to the paid license.

Shouldn't the credentials be tied under the registered Adobe email? Also, is my understanding correct that we should discontinue using the JWT_CLIENT_ID and JWT_SECRET_KEY?

Please advise.