Continue digital signature process for operation '&1'

What causes this issue?

A digital signature process is open for this notification, since a
multi-level procedure has been entered in Customizing.

System Response

It is not possible to process the notification.

How to fix this error?

You must continue with the signature process that has already started
for business status.

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.