After November 2020, APNS (Apple Push notifications) will no longer work in Sametime V9 or V10 environments. Apple will drop support for the legacy APNS protocol that is used in Sametime V9 and V10.
If you require mobile APNS (Apple Push Notification), Sametime will need to be upgraded to HCL Sametime v11.
Source: HCL Software Customer Support – KB0082262