Good day @aliosmanisik
Thank you for posting to the PayPal community.
The reference transaction is enabled for your sandbox account.
To resolve the 403 error you are currently facing, I would suggest to please contact your website developer or the third party eCommerce support to cross check your using same SANDBOX REST API Credentials(Client ID & Secret) while performing the below API calls.
https://developer.paypal.com/api/rest/authentication/
https://developer.paypal.com/api/rest/postman/
Also, If a third-party eCommerce partner is performing API operation on your behalf, you(i.e merchant) should be on-boarded and necessary API permissions should be granted to the Partner(API Caller).
https://developer.paypal.com/docs/multiparty/
https://developer.paypal.com/docs/multiparty/seller-onboarding/
Merchants can manually grant permission to a third-party eCommerce to access specific information in your PayPal account and perform PayPal API operations on your behalf.
Login PayPal.com >> Settings >> Account Settings >> Website payments >> API Access >> Pre-built payment solution >> Grant API permission >> contact your "Third party software eCommerce" for Third Party Permission Username >> enter the username.
Direct link - https://www.paypal.com/cgi-bin/webscr?cmd=_profile-api-grant-authorization
https://developer.paypal.com/api/nvp-soap/paypal-payments-standard/admin/third-party/
Note: For LIVE accounts, I would suggest to please contact our PayPal Customer service via link - https://www.paypal.com/smarthelp/contact-us (then choose at the bottom one of the contact methods - email or phone) who should be able to help you regarding the request.
If your still facing issues, please create an MTS ticket via - https://www.paypal-support.com/s/?language=en_US with the detailed information and error details.
Sincerely,
Kavya
PayPal MTS
If this post or any other was helpful, please enrich the community by giving kudos or accepting it as a solution.
