Security header is not valid

Hi there, thank you for reaching out to the Paid Memberships Pro team.

After several weeks of building a site with membership management, everything was ready, packages were defined, PMPro pages, email templates, payment methods, translations and a separate membership area with many user fields were set up.
Everything perfect on XAMPP.
But live we are now faced with the last mistake before I give up.

On XAMPP like Live we have PayPal Express running in sandbox mode with the API data such as username, password, signature. The test payments on XAMPP run perfectly – LIVE comes with the same data: “Security header is not valid”!?

How can it be that everything runs perfectly from a local development computer and not from the 100% identical live website?

In addition, it does not work with newly generated NVP/SOAP API integration data: Same error.

Please do not give advice like: “contact PayPal Business Support”. I already have it and as expected it won't lead to anything.
We also have the https://www.paidmembershipspro.com/security-header-is-not-valid/.

As you have gone from staging to live mode, this error is typically caused by invalid credentials being used.

Please ensure that live credentials are being used in live mode.

If this is still the case, I have to unfortunately suggest reaching out to PayPal support as we only use the credentials provided – the error itself originates from PayPal.

Kind Regards,
Jarryd
Support Manager at Paid Memberships Pro

Nein, es wird und wurde weiterhin die Sandbox verwendet, nur wurde die gesamte Website inzwischen vom XAMPP zu einem Live Host übertragen. Es ist also eine 1:1 Kopie und alles l?uft.
Die Daten stimmen sicher, sie werden auch in anderen Anwendungen verwendet und dort gibt es keine Fehlermeldung.

Ich habe auch kurz zum Live Modus gewechselt, natürlich mit den Live API Zugangsdaten: Selbiger Fehler.
Und diese Live Daten funktionieren seit 2007(!) bei diversen gro?en Shopping Anwendungen uvam.

der Fehler selbst stammt von PayPal.

Sicher.
Und ich wei? (eben vom Business / H?ndler Support) das die bei PayPal seit einiger Zeit vieles ver?ndern.
Egal ob die “No-Code” Buttons, Zahlungslinks oder API: So manches Layout, aber auch Funktionen wurden (ohne Vorankündigung) ver?ndert.
Und: Es gibt jetzt dadurch Probleme bei der Erkennung der Endger?te und bei der Verifizierung des Ursprungs der Zahlung.

Also liegt das oben erw?hnte Problem mehrheitlich bei PayPal. Was die aber nie zugeben werden, egal wie oft ich/wir denen noch schreiben. Auch da sind immer die anderen Schuld ..

Wir müssen da Projekt nun auf Eis legen und die Mitgliedsbeitr?ge weiterhin offline einziehen. PayPal ist in Verbindung mit PMPro leider so nicht machbar und einen anderen Zahlungsanbieter haben und wollen wir nicht.

No, the sandbox is still being used, but the entire website has now been transferred from XAMPP to a live host. So it's a 1:1 copy and everything works.
The data is certainly correct, it is also used in other applications and there is no error message there.

I also briefly switched to live mode, of course with the Live API access data: Same error.
And this live data has been working in various large shopping applications and much more since 2007(!).

the error itself comes from PayPal.

Secure.
And I know (from business/merchant support) that they have been changing a lot at PayPal for some time now.
No matter whether the “no-code” buttons, payment links or API: some layouts and functions have been changed (without prior notice).
And: This means that there are now problems with recognizing the end devices and verifying the origin of the payment.

So the problem mentioned above is mostly due to PayPal. But they will never admit it, no matter how many times I/we write to them. It's always someone else's fault...

We now have to put the project on hold and continue to collect membership fees offline. Unfortunately, PayPal is not possible in conjunction with PMPro and we do not have or want to have another payment provider.

Please navigate to Memberships > Settings > Payment Gateway and remove the credentials that have been entered. Save the empty fields.

Head back over to PayPal and follow the same steps to obtain your credentials – regenerate or recreate the signature this time. Copy and save those credentials back into Paid Memberships Pro.

Please give this a try and let me know if it helps.

Kind Regards,
Jarryd
Support Manager at Paid Memberships Pro

Das habe ich mehrmals alles so gemacht: Es hilft nichts.
Und natürlich wei? der PayPal Support auch keinen Rat.
Aber wie gesagt, die Onlineüberweisung ist für dieses Projekt vorerst eingestellt.