&1 partners were deleted

What causes this issue?

The partner determination procedure changed as a result of the change
to the notification type. The partners that were not planned in the new
partner determination procedure were deleted.

System Response

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

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.