The article describes the license update process after renewing the license for Corero.

The customer may receive notification that the license is expired while logging in.

Whenever the customer renews their contract, they'll have new PO with new SSRN. All of them are kept track on Corero system.
Nevertheless, Corero issues license according to the FIRST original SSRN (find at CMS > Licensing page).

Corero won't need to replace license in case of SSRN change. Although customer may see "Expiry date = None", they won't be able to use in case of the contractual end date is expired - Corero has own way to manage.

Please open a Corero ticket for any further clarification.