Valid date date of assignments must be the &

What causes this issue?

There are assignments that begin before the main assignment. This is not
permitted because the main assignment must always begin before and end
after all secondary assignments.

System Response

The system cannot copy the entered assignments.

How to fix this error?

Adjust the "Valid from" date of the secondary assignments to begin on
the same date as the validity period of the main assignment, or adjust
the "Valid from" date of the main assignment so that it begins before
all other assignments. Alternatively, set the "Main Assignment"
indicator for the assignment that begins first.

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.