My lumia 930 win10 didnt also open whatsapp.
The screen says ''loading'' and after a couple second it goes back too the start screen.
I restart the phone,look for updates (no update available) en remove end reinstall whatsapp a several times, it DIDNT WORK!
I think its a Windows issue, not whatsapp...
Yep It's a error with OS.. Friends, Are there not clever enough software developers in Microsoft to fix this issue..for windows phone lovers in the whole world..with this issue my phone is worthless.. ☹☹☹