Why won't my messages app open?

[iMore Question]

whatsapp messages won't open

I updated my I-phone 5 software to ios8.

Since then when I open messages from certain contacts it does not open, but defaults back to the I-phone main screen i.e. exits Whatsapp.

What seems to be the problem and fix?

 

[phreddyl]

Re: whatsapp messages won't open

I believe this is a repeat thread but delete the app and re install