"The transaction did not complete with the customers selected payment method. Instruct the customer to retry the transaction using an alternative payment method from the customers PayPal wallet. The transaction did not complete with the customer's selected payment method"
The reason why the transaction was denied can only be provided or explained by PayPal. Please, contact PayPal directly to determine why the transaction was denied.
See more information from PayPal in this article.
As a workaround you may update your billing method and pay with credit card or by bank transfer.
Here is how: Making changes to your Billing Account