paypal chained payment " 520003 - Authentication failed. API credentials are incorrect.&quot

Hi again,

i am trying to set up paypal chained payments and when even i try to do any transaction in the live environment or sand box I get the mentioned problem.

my app with paypal is "approved conditionally". not sure if its because of this of my settings.

for sandbox testing i have made 3 accounts 2 business account and 1 person account.

i have gone through many post on the forum and tied to follow the instruction but having the same problem.

i have set up my application at
i have gotten my API username and signature from

best regards,