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.
