attempt to call global 'SendAddonMessage' (a nil value)

[Thrumbar]

Get this when requesting others to follow...
Debug to chat says
Sending follow command to party
SendAddonMessage Follow FOLLOW PARTY

Message: Interface\AddOns\Hydra\Core.lua:69: attempt to call global 'SendAddonMessage' (a nil value)
Time: Fri Jul 20 01:23:49 2018
Count: 18
Stack: Interface\AddOns\Hydra\Core.lua:69: attempt to call global 'SendAddonMessage' (a nil value)
Interface\AddOns\Hydra\Core.lua:69: in function `SendAddonMessage'
Interface\AddOns\Hydra\Modules\Follow.lua:213: in function `HYDRA_FOLLOWME'
[string "HYDRA_FOLLOW_ME"]:2: in function <[string "HYDRA_FOLLOW_ME"]:1>