The license key for Sitecore Identity Server 7.x expires on October 28, 2023. If not updating the license key by the expiration date, a warning message might appear in the logs. The warning message can be safely ignored because it will not impact the functionality of Sitecore Identity Server.
To resolve the issue, use a new license key. In the root folder of the Sitecore Identity Server instance, replace the existing Duende_License.key file with the following file: Duende_License.key.