What causes this issue?

Generation of postings from payment requests requires certain
customization and variant creation. In this case, the program Rfebfw00
requires a variant which identifies the type of payment order to create
from the payment request.

System Response

Program requires this variant. Create it and restart the transaction

How to fix this error?

Visit program Rffdza00 and create a variant named SAP_RFEBFW00

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.