I received API credentials but I need an Application ID to send Adaptive Accounts API Requests.
I used their sandbox app ID: APP-80W284485P519543T.
Now it's time to go live.
Unfortunately, Adaptive Payments and Adaptive Accounts are deprecated, and can no longer be used for new integrations.
Instead, PayPal will tell you to use a supported integration such as PayPal Checkout. You can find a front-end demo here:
Version that calls server-side routes to create and capture a v2/order via APIs: https://developer.paypal.com/demo/checkout/#/pattern/server
Version that does not do that, and instead only uses client-side HTML/JS: https://developer.paypal.com/demo/checkout/#/pattern/client