1) There should not be any punctuation marks on the phone number. For example, 5556425562 is correct when (555) 642 - 5562 is incorrect.
2) First off, ensure that you are copying and pasting the credentials in correctly from Twilio. You should be getting the information from Programmable SMS -> Dashboard -> API Credentials as depicted in the image below. Double check all numbers and letters. Please note that the following is a sample and will cause an error if you attempt to use it in your own booth.
3) You should have put money into your account. If you haven't, click on your e-mail in the top right hand corner and upgrade. You only need $20 in your account.
4) If it's still not working, test your internet connection and see if you are connected to the internet.