Cost center & is invalid

What causes this issue?

The cost center which you have entered is not valid.

System Response

Check whether you have entered the cost center correctly. If necessary,
correct your entry.
If you have entered the correct cost center, check whether
the validity period of the cost center is sufficient,
the cost center type allows production,
you can post actual costs to the cost center.

Error message extract from SAP system. Copyright SAP SE.