3305887 - Error: "The status of this change number does not allow you to set it to active."

When you try to activate a change number in SAP ECTR it fails with the following error:

E02514 = Der Status dieser Änderungsnummer erlaubt Ihnen nicht diese aktiv zu setzen.
E02514 = The status of this change number does not allow you to set it to active.
E02514 = 此更改號碼的狀態不允許您將其設為啟用中。
E02514 = 不允许将此更改编号的状态设置为活动。

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KBA , PLM-ECC , SAP Engineering Control Center (SAP ECTR) , Problem