Can`t send message to public chat

I'm trying this one command to test sending from cli

`zbxtg.py "@xxx" test test`

where @xxx is my personal profile, and I'm receiving new message from @MyAlertingBot to my personal account (@xxx)


But if I am trying

`zbxtg.py "@yyy" test test`

where @yyy is public channel, I'm getting this error
`zbxtg.py: You need start a conversation with your bot first in '@yyy' group chat, type '/start@MyAlertingBot'`

After sending "/start@MyAlertingBot" message in @yyy chat nothing happens.

At the same time alerting from graylog via @MyAlertingBot to @yyy works well...

I have read all the wiki pages and all the repository files, but can`t find the answer.

_Reinviting @MyAlertingBot to @yyy chat has no effect_
_zbx_tg_tmp_dir is 100% writable, becase new file was created there after first zbxtg.py script call_

My config: (zbx_server_version 4)


Debug info: