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Go to Admin panel > Store > Configuration > Sales Payment Method > Choose PayPalAdmin Panel > Store > Configuration > Sales Payment Method > Choose PayPal (existing PayPal method which enable in fronted for example Payments Standard)

  1. Email Associated with PayPal Merchant Account -> It should be valid PayPal Merchant Account.
  2. API Username -> It should be valid API Username.
  3. API Password -> It should be API Password.
  4. API Signature -> It should be API Signature.
  5. Enable this Solution -> It should be Yes.

Note:- All above filed should be valid credentials.

Go to Admin panel > Store > Configuration > Sales Payment Method > Choose PayPal (existing PayPal method which enable in fronted for example Payments Standard)

  1. Email Associated with PayPal Merchant Account -> It should be valid PayPal Merchant Account.
  2. API Username -> It should be valid API Username.
  3. API Password -> It should be API Password.
  4. API Signature -> It should be API Signature.
  5. Enable this Solution -> It should be Yes.

Note:- All above filed should be valid credentials.

Go to Admin Panel > Store > Configuration > Sales Payment Method > Choose PayPal (existing PayPal method which enable in fronted for example Payments Standard)

  1. Email Associated with PayPal Merchant Account -> It should be valid PayPal Merchant Account.
  2. API Username -> It should be valid API Username.
  3. API Password -> It should be API Password.
  4. API Signature -> It should be API Signature.
  5. Enable this Solution -> It should be Yes.

Note: All above filed should be valid credentials.

2 Edited the content for better view
source | link

Go to Admin panel >>> Store >>> Configuration >>> Sales Payment Method >>> Choose PaypalPayPal (exiting Paypalexisting PayPal method which enable in fronted for example Payments Standard)

1.>> Email Associated with PayPal Merchant Account -> It shoud be valid PayPal Merchant Account.

2.>> API Username -> It shoud be valid API Username.

3.>> API Password -> It should be API Password.

4.>> API Signature -> It should be API Signature.

5.>> Enable this Solution -> It should be Yes.

  1. Email Associated with PayPal Merchant Account -> It should be valid PayPal Merchant Account.
  2. API Username -> It should be valid API Username.
  3. API Password -> It should be API Password.
  4. API Signature -> It should be API Signature.
  5. Enable this Solution -> It should be Yes.

Note:-Note:- All above filed should be valid credentials.

Go to Admin panel >> Store >> Configuration >> Sales Payment Method >> Choose Paypal (exiting Paypal method which enable in fronted for example Payments Standard)

1.>> Email Associated with PayPal Merchant Account -> It shoud be valid PayPal Merchant Account.

2.>> API Username -> It shoud be valid API Username.

3.>> API Password -> It should be API Password.

4.>> API Signature -> It should be API Signature.

5.>> Enable this Solution -> It should be Yes.

Note:- All above filed should be valid credentials.

Go to Admin panel > Store > Configuration > Sales Payment Method > Choose PayPal (existing PayPal method which enable in fronted for example Payments Standard)

  1. Email Associated with PayPal Merchant Account -> It should be valid PayPal Merchant Account.
  2. API Username -> It should be valid API Username.
  3. API Password -> It should be API Password.
  4. API Signature -> It should be API Signature.
  5. Enable this Solution -> It should be Yes.

Note:- All above filed should be valid credentials.

1
source | link

Go to Admin panel >> Store >> Configuration >> Sales Payment Method >> Choose Paypal (exiting Paypal method which enable in fronted for example Payments Standard)

1.>> Email Associated with PayPal Merchant Account -> It shoud be valid PayPal Merchant Account.

2.>> API Username -> It shoud be valid API Username.

3.>> API Password -> It should be API Password.

4.>> API Signature -> It should be API Signature.

5.>> Enable this Solution -> It should be Yes.

Note:- All above filed should be valid credentials.