MarketPress error with PayPal Standard: 520003 - Authentication failed. API credentials are incorrec

I have MarketPress, it is configured and looks great with some new shortcodes and the products listed. Thanks!

I have set up Google Checkout successfully, however PayPal standard is not configuring properly for some reason.

For PayPal standard, the chained set up should only require my PayPal user name (email address) and be set to live (it is). PayPal standard is configured on PayPal, I believe. I have not seen anything on their side to use sandbox with just the email credentials. Being that the API version is neither available to me via PayPal and not set up in MarketPress, why would I be getting the error: '520003 - Authentication failed. API credentials are incorrect.'?

Thanks so much,


  • Arun Basil Lal
    • New Recruit

    Hey @jcaynes

    I am confused here, Are you using the Sandbox mode or Live mode?

    Have you filled in the API credentials? If you are using the live mode, have you created the application? You have instructions on how to do that, on the settings page, See the screenshot attached.

    Let me know.

  • jcaynes
    • WPMU DEV Initiate

    Only way to get around this so far has been to enable PayPal Express on the multi site. After enabling PayPal Express I can no longer use any other payment methods like my own cc processing gateway or Google Checkout. Is there any way to allow for more options?

  • Paul
    • The Green Incsub

    @jcaynes, I'm sort of confused also. If you are attempting to use PayPal chained payments this will disable other payment gateways on the sub sites. The purpose of using the PayPal chained is specific to the global cart option on the MarketPress Network setup.

  • jcaynes
    • WPMU DEV Initiate

    I think the first issue is determining what chained payments relate to as far as PayPal is concerned. I tried standard PayPal on subsites where I would only need an email address for validation - this seemed to correlate to the "chained payment" selection offered in marketpress. This didn't work.

    I received errors for an API, which I didn't have set up on PayPal yet (because I was set up under PayPal standard only). In working through the issue, I set up PayPal Express, added the API in the marketpress network admin under PayPal Express and now cannot use any other payment methods.

    I would prefer to have multiple payment options rather than be exclusive to PayPal Express. I would like options such as Google Checkout and a credit card payment gateway in order to broaden customer payment options. Not everyone wants likes or uses PayPal.

  • aecnu
    • WP Unicorn

    Greetings jcaynes,

    Thank you for your additional feedback and input, it is greatly appreciated.

    After reviewing this entire ticket and your thoughts in your last post there seems to be a big miscommunication as to what/how this all works.

    The facts of the matter are that chained payments must have an API which is created and approved at PayPals, then issued a PayPal APP ID by PayPal specifically for chained payments - it is not related to the API within your PayPal profile on the PayPal website.

    Chained payments is specifically used for creating a store that takes a commission of the sales of the products sold within the store or stores. No other purpose and can not be mixed with other store types.

    However, in a standard store setting without the commission of sales model being used, one can use a combination of the gateways (excluding chained payments) to include PayPal Express, Google Checkout, etc. and the end user chooses which to pay with during the purchase cycle.

    In summary:

    Commission based store(s) model = chained payments.

    Other store model = the ability to have mix and match payment gateways including PayPal but not chained payments.

    I hope this helps clarify the payment gateways and chained payments and how they may or may not interact together.

    Thank you for being a WPMU Dev Community Member!

    Cheers, Joe

  • aecnu
    • WP Unicorn

    Greetings Jan,

    Thank you for this great question

    Yes this could be used when network activated.

    To try to clarify a little more, you can run Market Press fulfilling a few different types of business models and certainly some i have not thought of at the moment.

    However, the three most common types would probably be:

    a) Your own store or affiliate marketing stores. (it is just your efforts in this scenario)

    b) You can sell stores/web sites straight out, perhaps for a recurring monthly fee.

    c) You can have a series of stores but instead of charging a monthly fee, you charge a percentage of the sale. This is where PayPal chained payments comes in and the only place where it is used or relative.

    In the other scenarios mentioned above you can use any or all of the other payment gateways that you would like with the exception of PayPal chained payments.

    You can allow your "store owners" ( b above ) to have their choices or limit the available gateways as well not including chained payments.

    So in summary:

    You use PayPal chained payments when selling or providing Market press stores to others based on a commission based on sales business plan.

    With the other business plans, it is a mix and match as you see fit.

    On a side note, when you respond to a ticket mark resolved, please check mark the not resolved box below or we may just miss the reply not answering because we and the ticket system then see and think the ticket is indeed resolved.

    It is no big deal doing marking the ticket as not resolved and posting your question or whatever. But it could be a big deal for you if you believe we are ignoring you or just not answering your additional questions.

    Cheers, Joe

  • whatsup
    • WPMU DEV Initiate

    Hello. I'm getting what I need to do - go to and set up my app. Problem is none of the links from my site in the Settings page go to live URL. All are broken.

    The link "register then submit your application" leads me to a broken link!input.jspa

    The "more information" link leads me to another broken link

    So, I would be grateful if someone could be very basic with the instructions on how I need to set up my payment system.

    Thank you.

  • Timothy
    • Chief Pigeon

    Hey there.

    Thanks for responding hpidriver!! :slight_smile:

    Hey Crissie, thanks for posting in this thread, however it might be best if you open your own, even if the issues seem closely related. That way it will remain independent of this one and ensure it doesn't confuse issues here if this thread needs reopening again by the author.

    Posting on old threads can also lead to us missing your questions.

    It also means the member who started this thread or anyone following it isn't inundated with post notifications each time we respond to each other. A lengthy thread could annoy the original

    This also allows us to better track and answer your questions to ensure we don't miss any for ya.

    If you still need help after hpidriver's response, you can start a new thread here:


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