Most probably this error happened because you had generated an Apple Pay certificate using the Paytabs merchant profile which is not the same profile that initiated the payment.

In this article you will learn about: 

How to investigate the reason that caused this error?

You can investigate the reason for such an error from the "API debug log", by navigating to the Developer’s menu > Testing > API Debug Logs (within your desired profile).

Reason #1: The uploaded certificate doesn't match the profile generated in the first place.

To manage the Apple Pay certificate in your PayTabs dashboard, you have to:

1. Generate a certificate (on the Paytabs side)

2. Upload the certificate to the Apple Pay side3. Generate a certificate on the Apple Pay side and download it

4. Upload the generated from step (3) to Paytabs Dashboard

For more details, check the article How to configure Apple Pay Certificate in my PayTabs dashboard? 

Steps (1) and (4) should be done using the same PayTabs merchant profile. if it doesn't match, you will receive the error "Profile mismatch"

The solution for that is to follow the steps (as mentioned above) in the article again and to use the same Profile on downloading the generated certificate, and on uploading the Apple Pay one.