Connected to wi-fi but Whatsapp messages won't send My phone is connected to the wi-fi but my Whatsapp messages won't send.  They have a clock icon next to them.
First wait for sometime, while device is connected to wifi and it starts to auto update apps and uploading/syncing of local data backup such as photos, notes, contacts get started.

If you're seeing a syncing sign  on the top of the screen as shown in picture then wait for sometime until process ends.



Alternatively, the other major thing could be settings turned on that is "stop app using data in background".

I use above settings to prevent specific apps from using heavy data in background.

Read the linked article.