Error processing checkout. Please try again.

I am trying to integrate a payment gateway of my country, to the donation system. This payment gateway is integrated with WooCommerce, but with the donation system is not integrated, I tried to change the styles and I keep getting “Error processing checkout. Please try again”. And checking with style 4, the payment method does not exist despite being correctly integrated with WooCommerce. Also, I got a message asking me to contact support to fix that kind of problem.

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