No start date maintained for equipment &1

What causes this issue?

Neither the start date, nor the effective start date is maintained for
the given equipment.

System Response

Maintenance plan cannot be generated for this equipment.

How to fix this error?

Go to the MP Header & Item tab and maintain the start dates for
all technical objects.

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.