The earliest recollection of this bug is traced back to PAN-OS 9.1.0 - July 29, 2024. This bug is fixed in PAN-OS versions 9.1.0. Fixed an issue where third-party VPN clients were unable to connect to GlobalProtect using IPSec due to a stale IKE/IPSec security association (SA). For more information: https://docs.paloaltonetworks.com/pan-os/9-1/pan-os-release-notes/pan-os-9-1-addressed-issues/pan-os-9-1-0-addressed-issues