In Unity i can't get channel from which user came using branch.io

Question

In Branch my partner management is Google AdWords. Here i initalize branch and trying to get user's channel. In branch i get event named FIRST_OPEN_FROM_ without channel

private async void Start()
    {
        Branch.initSession(CallbackWithBranchUniversalObject);
        int status = await _backendAPI.GetStatusFromAPI();
        Debug.Log("status = " + status);
        if (status == 200)
        {
            _appUnblocker.UnblockAppForModerator();
        }
        if (PlayerPrefs.HasKey("filesOpened") && PlayerPrefs.GetInt("filesOpened") == 2 && !PlayerPrefs.HasKey("userRated"))
        {
            PlayerPrefs.DeleteKey("filesOpened");
            OneSignal.InAppMessages.AddTrigger("ratingSuggestion", "true");
        }
    }

void CallbackWithBranchUniversalObject(BranchUniversalObject buo, BranchLinkProperties linkProps, string error)
    {
        if (error != null)
        {
            Debug.LogError("Error : " + error);
        }
        else
        {
            Debug.Log("channel = " + linkProps.channel);
            PlayerPrefs.SetString("channel", linkProps.channel);
            PlayerPrefs.Save();

            if (!PlayerPrefs.HasKey("firstOpenBranch"))
            {
                PlayerPrefs.SetString("firstOpenBranch", "true");
                BranchEvent e01 = new BranchEvent("FIRST_OPEN_FROM_" + linkProps.channel);
                e01.SetDescription("test event to check channel channel = " + linkProps.channel);
                e01.AddCustomData("channel", linkProps.channel);
                Branch.sendEvent(e01);
            }
        }
    }

I wrote in branch.io support but didnt get anything useful.