It does appear you are synced to the forums. To use /cow you do need to be synced to the discord as well. You can sync to the discord by doing /sync in game and selecting the discord icon. You will then put the !sync <code> In the sync channel on discord.
If you are already synced to the discord you can always try to resync your forums and discord account again.
To re-sync to the forums you will first need to unsync your account to do that you will need to access your MineSync Settings found at the top of the screen.
After selecting MineSync settings You will click Unlink account
Then you will sync your account the same way as you did the first time.
You will need to go to the #bot channel and type !unsync This will unsync your account from the discord where you can then re sync your account the same way as explained above