Hi, thank you for your answer. Yes, i tried to remove app and reinstall it again.
yes, i also checked all possible notification settings (both for app and OS). Unfortunattely without success.
What i realize:
1) Even when I am using WIFI connection, i don't have notification (with active Vodafone sim card)
2) When i physically remove Vodafone sim card, Whatsapp start working fine (with only WIFI connection)
3) When i use another sim card with this phone and whatsapp account, whatsapp works fine (with the same settings, so i just changed Vodafone sim card to KPN or Lebara) both with WiFi Active/non active.
So i believe that something goes wrong with Vodafone settings on my phone. For me there are two things quate strange:
1) data tried to pass via GSM even with strong wifi connection (just to be sure, i switched off option which is allows to use GSM in case of poor WiFi Signal)
2) No (or with 10/15 minutes delay) notifications about new messages from whatsapp (in the same time Viber, Skype, Facebook messanger work fine).
I already tried all Whatsapp recommendations (remove live icon, add a keyboard language, switch on Battery saver and off. Switch Off whatsapp notifications and return back to ON. Reinstall whatsapp). I don't have any additional software on my phone. And as i said, i tried two different devices. So i don't have other
PS I am using Nokia Lumia 735, Lumia 820, and Windows 8.1 update 2 (Lumia Denim)