Skype not notify of new messages until it is opened

My Skype is not showing new messages or Skype call until I open it. I have a Samsung J6+. It night be my fault due to changing many settings at once now causing Skype to behave this way. So it was with other chat messengers such as Wire and Whatsapp. But I got Whatsapp working fine now, when i disable "data saver" feature under "data usage". However Skype and Wire are not working as they should. Can anybody please help by provide a list of possible settings and solutions ? Thanks.