Client has status 'not modifiable'

What causes this issue?

The system administrator has set your logon client to the 'not
modifiable' status.
Client-specific objects can <ZH>not</> be changed in this client.

System Response

The function terminates.

How to fix this error?

Contact the system administrator.
For more information, see the <LS>SAP Library</> under <LS>Change and
Transport System</>.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.