Viber do not work in the background - iOS 10.3.2, help!

Hi guys,
I use Viber app on my Iphone 6 plus very much often, but suddenly a week or 10ish days ago I started to have a huge probem ( I suppose since I have installed iOS 10.3.2 )
My Viber app do not work in the background at all!
That means , I can use Viber only, but only if I open the app...in the meantime if someone sent me me message(s) or gave a call(s), I do not get any notification, and to other sides, it says I am offline ( last seen blah, blah )

That means, my Viber do not work, or simply said, stop working even if I go to another application, and do not totally close my Viber
Bottom line - My Viber app on iOS 10.3.2 on Iphone 6 plus works if open the app itself and use it !
If i close the app, or go back to another, Viber go to stop mode

I checked everything, but really everything - battery issues, background app issues - nothing happened

GUYS PLEASE DO HELP ME!
Thx

 

@ganja24 Do you have any idea how to solve this issue???