Whatsapp

Mohamme_2028649 Assuming that you are hoping to use it on mobile data, have you actually enabled mobile data? Are other internet sites working via the browser?

Have you checked whether WhatsApp is down ? 

Do you have good mobile coverage  in the area(s) you are trying to use Whataapp ?

If you are using Wi-Fi whilst trying to use Whataapp, is the Wi-Fi good ?

Have you checked in your phone’s App Store that you have the latest version of WhatsApp ?

Have you tried the old fix of switching your phone off and on again ?

Personally, although I use WhatsApp, as many of my contacts use the Meta / Facebook owned app, I find Telegram and Signal to be better apps, more robust with better call quality, and not owned by the same company that owns Facebook, Instagram and who knows what else.