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Stand Alone Transaction cannot be used with this feature. Make sure Stand Alone Transaction is unchecked inside of the campaign product.
First, contact PayPal and have the Reference Transaction Enabled enabled on their end your account if you are planning to enable rebilling or upsells with PayPal.
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Make sure you check the referenceTransactions box on your PayPal MID setup to enable rebilling and upsells for seamless checkout.
After enabling the referenceTransactions option on your PayPal MID, log into your PayPal merchant account and confirm that your account is configured correctly to support Reference Transactions.
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