The earliest recollection of this bug is traced back to PAN-OS 8.1.20 - January 09, 2024. This bug is fixed in PAN-OS versions 9.1.9, 8.1.20. Fixed an issue where the negative time difference between the dataplane and the management plane during the client certificate info check prevented the GlobalProtect client from connecting to the GlobalProtect gateway with the following error message: Required client certificate not found . For more information: https://docs.paloaltonetworks.com/pan-os/8-1/pan-os-release-notes/pan-os-8-1-addressed-issues/pan-os-8-1-20-addressed-issues https://docs.paloaltonetworks.com/pan-os/9-1/pan-os-release-notes/pan-os-9-1-addressed-issues/pan-os-9-1-9-addressed-issues