Deletion flag set for work center &1 plant &2

What causes this issue?

You have entered a work center that has been flagged for deletion.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

If this is an error message, you must correct the entries accordingly.
A work center can only be used if it has not been flagged for deletion.
If this is a warning, you can use the work center, but you should note
that this could result in problems during subsequent transactions in
which this work center is used.

Error message extract from SAP system. Copyright SAP SE.