The error is displayed as follows:
PayPal gateway has rejected request. The totals of the cart item amounts do not match order amounts (#10413: Transaction refused because of an invalid argument. See additional error messages for details).
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Go to Admin Panel > Store > Configuration > Sales Payment Method > Choose PayPal (existing PayPal method which enable in fronted for example Payments Standard)
Note: All above filed should be valid credentials.
Go to Admin panel locate navigation System >> Configuration >> Sales
Payment Method >> Choose Paypal (exiting Paypal method which enable in fronted for example Payments Pro (Includes Express Checkout)) >> find "Transfer Cart Line Items" choose option value : No