The first thing is to make sure your number has been entered correctly. US-based numbers are entered exactly as you would dial the number (including the preceding “1”), without special characters like hyphens or parenthesis (Ex: 14088675309). Phone numbers outside the US should start with the country code – without leading zeros or other special characters (Ex: 645233456 for New Zealand).
If your number is correct and it is still not working, it’s possible your carrier is not yet supported. If this is the case, check back in a few months. Our SMS partner is adding new carriers all the time. Here’s a shortcut to send yourself a reminder: firstname.lastname@example.org