Can't set webhook to viber bot

I have some troubles with setting webhook to my viber bot. Every time I wanna set my url viber api returns error. So I am trying to use this in postman:

Url: https://chatapi.viber.com/pa/set_webhook

{
    "url": "https://gutapi.ml/api/viber/post",
    "event_types":[
      "conversation_started"
   ]
}

When I use code below, viber api returns this result:

{
    "status": 1,
    "chat_hostname": "SN-CHAT-06_"
}

My url is valid and I have ssl sertificate, but it still does not work. Hope you'll help me