Hi,
It could be multiple reasons but try to work on below basics first:
Have you check the commit ID on both the peers ? Does they match?
BIG-IP 11.2.1 and later:
tmsh run /cm watch-devicegroup-device
BIG-IP 11.0.0 through 11.2.0:
watch_devicegroup_device
- Below elements must be correctly configured between both peers:
- Licensing and provisioning
- Software versions
- Management IP (must be unique)
- NTP
- ConfigSync IP
- Failover IP
- Ports( 443, 4353, 1026 (UDP), and 22)
- Device trust
https://support.f5.com/kb/en-us/solutions/public/13000/900/sol13946.html
https://support.f5.com/kb/en-us/solutions/public/13000/900/sol13946.htmlverifyingcommit