Here are some steps to help diagnose and resolve the problem:

1. Verify API Credentials:

2. Check Billing Agreement Setup:

{

"TOKEN": "BA-*********",

"TIMESTAMP": "2025-04-03T09:25:37Z",

"CORRELATIONID": "******",

"ACK": "Success",

"VERSION": "74.0",

"BUILD": "58807128"

}

Ensure that the ACK value is "Success" and that the TOKEN is correctly used in the subsequent redirect URL.

3. Inspect Redirect URL:

https://www.paypal.com/cgi-bin/webscr?cmd=\_customer-billing-agreement&token=BA-\*\*\*\*\*\*\*

Ensure that the token parameter matches the TOKEN received from the SetExpressCheckout response.

4. Consult PayPal's Documentation:

5. Contact PayPal Support: