Hello, If you're seeing a message that the credentials are invalid, there must be an issue either with the credentials you're using or the endpoint you're attempting to use them against. Transactions / API operations within our sandbox environment require API credentials from a sandbox account, you cannot use the credentials from a production account in our sandbox environment and vice-versa. Also check when copying / pasting the API credentials from PayPal, that no additional "blank" spaces are added at the end of each part of the API credential. This is common issue which occurs when copying / pasting the credentials. Check and double-check and credentials match exactly what is shown on PayPal and that you're using the correct API endpoint. Thanks !
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