Cannot use Whatsapp when on mobile data

[Android Question]

Hello,

Recently bought a Nexus 5... happy with all the other stuffs but the main problem that is occuring is that I cannot use whatsapp when I am on mobile data. Have tried all sorts of settings and asked my service provider too with the same but to no avail. Also, I was able to use whatsapp on my previous phone with the same service provider.

I can use web browser and other internet based apps when on mobile data, but can use whatsapp then and only then if I am on Wi-Fi... Is there some sort of settings needed to be done or any software crisis...??

Please advise me the needful.

Thanks and Regards