The license key for Sitecore Identity Server's dependent software Duende IdentityServer expired on October 28, 2024. This affects Sitecore Identity Server 7.0 and later versions. This expiry results in a warning message that appears in the logs. The warning message can be safely ignored because it does 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.
Note: This new license key is valid until November 18, 2027.