Hi Mohammad,
When you changed NTP, did you do this from the CLI of the AP?
Could you check what the NTP settings are in the Configure Tab -> Network Policy -> Additional Settings -> NTP Server
If OFF, it means the AP will use the manually set time you configure.
If ON, then the settings here will indicate which NTP server the AP and Network Policy Devices will use.
Please confirm that the settings here are accurate, and I would recommend enabling NTP in the Network policy if it's currently not enabled.
To make sure all APs know about this change, you could push a Delta(partial) update without requiring a reboot.
Hope this was helpful, happy to assist,
David Souri
HiveCommunity Moderator
