Requirement has been deleted, after ENTER you can recreate it

What causes this issue?

An independent requirement or a schedule line has already been created
and then deleted for this material.

System Response

The system saves independent requirements that were created under a
requirements number that is maintained internally within the system.
This requirements number is not deleted along with independent
requirements items. This means that if a planned independent
requirement item is deleted for a material, the requirements number
still exists. The system uses this requirements number to save new or
changed independent requirements for this material.

How to fix this error?

By selecting the ENTER key, you can create new planned independent
requirement items.

Error message extract from SAP system. Copyright SAP SE.