According to the get started documentation, the client id can be seen when the user open the deafult application generated by th platform when a new paypal developer account is created. Everytime I click it i get a 500 internal server error
Our apologies for the delay. We had a planned maintenance in sandbox environment on 15th June, so this is most likely why you were unable to view your REST app credentials. We are actively working on plans to migrate the PayPal legacy sandbox environment to a new data center. As part of this initiative, we scheduled several maintenance windows, where you may experience issues in sandbox environment. You can find more details about this in our sandbox migration bulletin.