Fiverr App Bug of notifications

[asimhamzagraphi]

Hello,
I am seller on fiverr for last 8 months. I am not sure this is fiverr side problem or something wrong with my phone but today I decided to discuss here. I donot recieve messages and notifications in my phone notification bar. Everytime I need to open the app and check either there is something new or not. And some times it directly sends all the notifications and messages of fiverr of last week which I already have seen.

I have set again and again my fiverr notification settings, phone notification setting and app settings but never got solution.

Note: It only happens when I am using phone data not Wifi. On Wifi everything works fine.