online active disconnected

Hi,

Which bigip version you are using?

If you are using 11.x please verify below link

https://support.f5.com/csp/article/K13946?sr=33711178cso

Please try below steps to fix HA and config sync issues.

1. Device Groups >put both boxes back to available.
2. Delete the existing device group.
3. Reset Device Trust. Choose Generate New Self-Signed Authority.
4. reboot the device
5. Device Trust>Peer list. Establish peering by giving right peer IP's.
6. Create device groups. "Sync-Failover". Put both devices in "includes". and check Network Failover (Network failover listen on udp port 1026)
7. Confirm both devices are in the Device List area.
8. Overview>(click self device)>choose "Sync Device to Group">Choose "Overwrite Configuration">Sync

***** Make sure both devices are using admin username for syncing and they should have same password*****

Hope this helps. If any issues please let us know.