Payment Action of Authorization is not allowed with Unilateral and Non-Credentialed authentication

[advcha]

Hello,

I got this problem when I use paypal express checkout on Magento 2.3. I tried to use sandbox. It seems run well. I can see the paypal login form popup and can login successfully. But after I click 'Pay' button and the popup is closed then I saw a flash error message on my Magento 2 site.

PayPal gateway has rejected request. PaymentAction of Authorization is not allowed with Unilateral and Non-Credentialed authentication (#10481: Transaction refused because of an invalid argument. See additional error messages for details).

Then I inspected the log file. I see the debug message but I have no idea what is wrong. Is this caused by Magento and/or paypal? Here is the debug message:

[2020-02-01 04:40:06] main.DEBUG: array (
  'url' => 'https://api-3t.sandbox.paypal.com/nvp',
  'DoExpressCheckoutPayment' => 
  array (
    'TOKEN' => 'EC-5TP478471D8088941',
    'PAYERID' => '5YLR7L3UWZK6Y',
    'PAYMENTACTION' => 'Authorization',
    'AMT' => '499.00',
    'CURRENCYCODE' => 'AUD',
    'BUTTONSOURCE' => 'Magento_Cart_Community',
    'NOTIFYURL' => 'https://xxx.com.au/paypal/ipn/',
    'RETURNFMFDETAILS' => 1,
    'SHIPPINGAMT' => '0.00',
    'ITEMAMT' => '499.00',
    'TAXAMT' => '0.00',
    'L_NUMBER0' => NULL,
    'L_NAME0' => '(CLEARANCE) Shoei J.O Hawker TC-1 Helmet - Red/Black',
    'L_QTY0' => 1,
    'L_AMT0' => '499.00',
    'BUSINESS' => NULL,
    'EMAIL' => 'xxx',
    'FIRSTNAME' => 'First',
    'LASTNAME' => 'Last',
    'MIDDLENAME' => NULL,
    'SALUTATION' => NULL,
    'SUFFIX' => NULL,
    'COUNTRYCODE' => 'AU',
    'STATE' => 'NSW',
    'CITY' => 'Melbourne',
    'STREET' => 'Second Ave.',
    'ZIP' => '3000',
    'PHONENUM' => '0489 849 999',
    'SHIPTOCOUNTRYCODE' => 'AU',
    'SHIPTOSTATE' => 'NSW',
    'SHIPTOCITY' => 'Melbourne',
    'SHIPTOSTREET' => 'Second Ave.',
    'SHIPTOZIP' => '3000',
    'SHIPTOPHONENUM' => '0489 849 999',
    'SHIPTOSTREET2' => '',
    'STREET2' => '',
    'SHIPTONAME' => 'First Last',
    'ADDROVERRIDE' => 1,
    'METHOD' => 'DoExpressCheckoutPayment',
    'VERSION' => '72.0',
    'USER' => '****',
    'PWD' => '****',
    'SIGNATURE' => '****',
  ),
  'response' => 
  array (
    'TOKEN' => 'EC-5TP478471D8088941',
    'SUCCESSPAGEREDIRECTREQUESTED' => 'false',
    'TIMESTAMP' => '2020-02-01T04:40:05Z',
    'CORRELATIONID' => '577d54e9fc5fa',
    'ACK' => 'Failure',
    'VERSION' => '72.0',
    'BUILD' => '54085969',
    'L_ERRORCODE0' => '10481',
    'L_SHORTMESSAGE0' => 'Transaction refused because of an invalid argument. See additional error messages for details.',
    'L_LONGMESSAGE0' => 'PaymentAction of Authorization is not allowed with Unilateral and Non-Credentialed authentication.',
    'L_SEVERITYCODE0' => 'Error',
  ),
)

I'd really appreciate if anybody can help. Thanks.