Sometimes when signing up to WhatsApp, you will receive the error:
We couldn't send an SMS to your number. Check your number and try again in 1 hour.
After trying the SMS and "Call Me" option on WhatsApp, if you are still not receiving the SMS or the phone call, go here:
https://www.whatsapp.com/contact
And complete the form with your email address and your 2ndNumber you are having trouble with. Be sure to use a genuine email address - do not use "spammy" email addresses such as ProtonMail and suchlike, as you will find the number permanently blocked.
For example:
Wait for WhatsApp to reply and authorise your number. This can take up to 72 hours so please be patient.
