Invalid Merchant Payments to this merchant are not allowed (invalid client id) in iOS Xamarin Forms

[Emmanuel2019]

I am doing iOS PayPal payment gateway integration ,when I'm adding my live account API credentials i am getting error message like "Invalid merchant".

For your reference please find the attached screenshot.

Error in my XCode debug area:

PayPal SDK: Request has failed with error: invalid_client - System error (invalid_client). Please try again later. (401) | PayPal Debug-ID: 740276c5705b9 [mock, PayPal iOS SDK 2.18.0] | Details: (
{
"error_description" = "Client Authentication failed";
}
).
2020-11-20 [Removed. Phone #s not permitted]0530 [5756:66691] PayPal SDK: Request has failed with error: invalid_client - System error (invalid_client). Please try again later. (401) | PayPal Debug-ID: c2f916428f798 [mock, PayPal iOS SDK 2.18.0] | Details: (
{
"error_description" = "Client Authentication failed";
}
).