The settlement run contains various merchant IDs

What causes this issue?

The settlement run contains payment card transactions with various
merchant IDs at the clearing houses. The settlement run can only
contain one merchant ID because a settlement of virtual cards (for
example SET) is going to take place.

How to fix this error?

Make sure that all payment card transactions in this settlement run use
the same merchant ID.

Error message extract from SAP system. Copyright SAP SE.