I'd have to see the log but if you're not receiving the SMS is maybe because Whatsapp can't send SMS to your country. Yappari doesn't have the voice registration method implemented (which is an alternative method for people that can't receive the SMS).

Anyway Whatsapp can send SMS to most countries so usually when people don't get the SMS is because they are entering the phone number in the wrong format, mostly because they don't know which is the correct format of their own number that international users need to know to send an SMS.

So 99% chances are you are entering the phone number in a local format (with a leading zero for example: 0234 4237898) or something like that.