Similar problem while upgrading from 11.4.1 to 11.6.0.
FIX: I had to renew license.
[root@xxx:INOPERATIVE:Disconnected] log tail -f ltm
<..>
Jan 17 08:06:48 xxx err mcpd[6458]: 0107142f:3: Can't connect to CMI peer 10.255.254.43, TMM outbound listener not yet created
Jan 17 08:06:53 xxx notice mcpd[6458]: 01071431:5: Attempting to connect to CMI peer 10.255.254.43 port 6699
[root@xxx:INOPERATIVE:Disconnected] log tmsh load sys config verify
Validating system configuration...
<..>
Validating configuration...
/config/bigip_base.conf
/config/bigip_user.conf
/config/bigip.conf
/config/bigip_script.conf
01070356:3: Load balancing feature not licensed.
Unexpected Error: Validating configuration process failed.