ERROR: 21661
Description
Phone numbers must be SMS-capable. Visit the phone numbers page of your account to view a list of phone numbers that you own and to determine whether they are SMS-capable.
Possible Causes
The number you are using is not capable of sending messages.
Possible Solutions
Check that you are using a Luubu phone number with SMS capabilities. You can see your purchased phone numbers and their capabilities in Settings Phone Numbers Manage Number +Add Number.
Purchase an SMS capable number from Settings Phone Numbers Manage Number +Add Number.