PayPal Here Android SDK Error - BadConfiguration: Cannot proceed with this merchant account

I'm trying to integrate the PayPal Here swipers into a Xamarin Android app. Everything is fine until I try and give my credentials to the SDK. Specifically, the line containing the call to PayPalHereSDK.SetCredentials

public void InitializeSdk( Context context, string serverName, string accessToken, string refreshUrl, string expires, IPayPalHereSdkWrapperCallback listener ) {
        PayPalHereSDK.Init( context, serverName );
        PayPalHereSDK.RegisterAuthenticationListener( this );
        PayPalHereSDK.CardReaderManager.RegisterCardReaderConnectionListener( this );
        if ( !string.IsNullOrEmpty( accessToken ) ) {
            var credentials = new OAuthCredentials( accessToken, refreshUrl, expires );
            PayPalHereSDK.SetCredentials( credentials, new SetAccessTokenResponseHandler( listener ) );
        }
    }

My SetAccessTokenResponseHandler class implements the Com.PayPal.Merchant.Sdk.Domain.IDefaultResponseHandler interface. As described above, the OnError function is called when call the PayPalHereSDK.SetCredentials function. I'm given the error code "BadConfiguration" and the message "Cannot proceed with this merchant account. ready"

I've searched Google high and low and, I believe, scoured SO pretty thoroughly. I can't seem to overcome the error, so I'm asking for help!

I'm not sure what exactly the issue was, but I ended up deleting the Sandbox App in my PayPal dev portal and creating a new one. Everything works now. head scratch

I resorted to this because, while trying to follow Sundar's suggestion, I started getting an "invalid scope" error. I had received them before and KNEW I had it fixed ( and no code had changed ). When I deleted/recreated the app, that error went away. Frustrating, but that's what worked!