WHMCS Paypal Checkout addon Signature Verification Failed

[Furkann]

Even though I did everything right, I encounter this on the "gateway log" screen.

When I check the logs, I see a result like this.

Don't be fooled by the time difference. They both ultimately mean the same thing. How can I find a solution without affecting my current customers?

[leemahoney3]

Did you check the docs here?

 

Quote

Signature Verification Failed

Signature Verification Failed indicates a problem in the payment notification anti-spoof verification. When a payment notification is received from PayPal, WHMCS makes an API request to PayPal confirming that the notification originated from PayPal.

Seeing this typically indicates that a subscription renewal payment was made through a different integration app from the one currently linked to your WHMCS installation.

This situation can arise if Unlink PayPal Account on the module configuration was used after the PayPal subscription was originally created. Once the unlink function is used, the subscription payments that pre-date it can no longer be recorded in WHMCS. Such subscriptions will need to be cancelled via the PayPal website. Clients can then create a new subscription under the current integration app linked to your WHMCS installation when their next invoice is due.

 

[Furkann]

At first, the solution in the documentation seemed like a ridiculous solution, and I did not want to implement it because I would have to create the renewed payments again. However, unlink and link Paypal works.

[leemahoney3]

5 minutes ago, Furkann said:

At first, the solution in the documentation seemed like a ridiculous solution, and I did not want to implement it because I would have to create the renewed payments again. However, unlink and link Paypal works.

It's unfortunate there isn't another way to do it, however I believe security comes first and therefore its necessary. Glad you got it sorted.