Apple Push Notification service (APNS) certificate for HCL Sametime Proxy 11.6 will expire 4/8/2022. Installing HCL Sametime Proxy 11.6 IF2 will update APNS certificate to expire 3/6/2023.
See Upgrading HCL Sametime 11.x Servers for upgrade steps. The upgrade will overwrite the web.xml file. If customized, restore from backup after upgrade is complete.
Chat only deployments without a Meetings server will require an additional step after applying 11.6 IF2 documented here.