Change number & does not allow you to create new BOMs

What causes this issue?

You want to use change number &V1& to create a BOM. However, this
change number does not allow you to create new BOMs.
One of the following situations triggered this error message:
The corresponding obejct type (eg. BOM, routing/plan) is not active in
the change master, so creation of new data or changes for this object
type are not possible using this change number.
The object type is currently locked for creation of new data or
changes in the change master.

How to fix this error?

Check your entries.
If you really want to create the BOM using the change number entered,
consult your system manager responsible for change master records to
get the change number adapted to suit.
Otherwise, enter another change number which does allow you to create
new data or make changes for the corresponding object type.

Error message extract from SAP system. Copyright SAP SE.