Currently I see only 3 choices in “Select Gateway Provider:” combobox in https://store.com/ Admin/Store/Payment.aspx. They are: Don’t accept Credit Card, Authorize.Net, and PayPal PaymentsPro DirectPay.  How can I add PayPal Standard to this list?  Right now when someone tries to enter credit card details via my web site to pay it always throws back an error code: This transaction cannot be processed due to an invalid merchant configuration. ( ErrorCode: 10501". Please try again later. ) When I look on the PayPal error codes page it just said: "Occurs when the billing agreement is disabled or inactive." I spent several days trying to solve this problem, don’t know what to do. Thank you.

Was it working before? PayPal Standard is the third tab in the payment section.

I set it up in the third tab properly, based on information from my PayPal Standard account, but I couldn’t enable this option (PayPal Standard) in in “Select Gateway Provider:” combobox for Credit Card providers (on the 1st tab for Credit Card payments). Only “PayPal PaymentsPro DirectPay” is available. And also after I enabled PayPal Standard on the third tab, I got extra tab in Process Order page, in addition to PayPal express button. I only need PayPal express button.

Please don't confuse PayPal Standard with Credi card payment. There is a reason why it's on its own tab. Just check "Enabled" checkbox will enable it.

I enabled Credit Card on the first tab. For “Select Gateway Provider:” I could only select (from the combobox) “PayPal PaymentsPro DirectPay”. I do not have PayPal Pro on PayPal.com (only PayPal Standard). Now when the customer tries to use Credit Card option, the error appears: This transaction cannot be processed due to an invalid merchant configuration. ( ErrorCode: 10501". Please try again later. ). Maybe I should use PayPal Standard for Gateway Provider (but it is not in the list of choices in combobox).

If you don't have PayPal Pro why do you enable it in Credit Card tab? Please disalbe it because you don't credit card merchant account.

I disabled it now, thank you. I just want to ask why there is no Paypal Standard option in "Select Gateway Provider" combobox on Credit card tab? Is it possible for me to add this option?

As I said many times PayPal Standard is not credit card merchant account. The checkout steps are completely different. User gets redirected from PayPal website.

Thank you. Now it's clear. I will use PayPal Standard as the only option for my web site. Inside PayPal web site the user can select credit card or his/her PayPal account payment options. It works for me too.