i think i have the same problem. i switched between N9 and N8. im pretty sure it is a client side problem because i still can register with my N8 but it fails on N9 with Wazapp and N900 with Yappari. I already contacted whatsapp and they reset my number but that didnt help either. i also reported the issue to tgalal and he said he will try to fix it.

so i we will have to wait for the next update that hopefully will fix the issue. meanwhile using ebuddy and its sucks big time.