TopView unable to send SMS via Twilio
If you are seeing messaging fail from Twilio suddenly after working for a long time, you may need to register your account through Twilio for Application 2 Person messaging.
Due to US carriers trying to regulate spam, Twilio has companies using their service conform to this registration requirement from the carriers. More information can be found in their explanation article: Programmable Messaging and US A2P 10DLC | Twilio.