Error Code: 10501

That error means that DoDirectPayment is not active on the account you’re trying to use it with.

Have you applied for Pro and activated it on the account yet? If so, it could be that you need to be using PayFlow instead of DoDirectPayment.

I did not sign up Pro yet, Papal express checkout is active. Can I used both Express checkout and DoDirectPayment?

Yes, you would use both together, but you need to have Pro active on the account before DoDirectPayment will work.

Until then, you could just enable Express Checkout and people can still pay with a credit card that way (even without a PayPal account) but the checkout would redirect through PayPal’s checkout pages instead of using the WooCommerce checkout page.

I’m going to close this ticket, but if you need help getting Pro setup let me know, or if you have any other troubles feel free to create a new ticket.