The most common reason why texts are not getting delivered to customers is because the shop's Twilio registration is not yet approved. You can check your Twilio registration status by navigating to your User Icon > Shop Settings > Shop Info page.
In order to send outbound texts to customers, you must first register for Twilio messaging and be approved following A2P 10DLC registration compliance.
For more information on text message registration with Twilio and how to get approved, click here.
If your Twilio registration is showing approved and your customers aren't receiving your texts, please contact support for further assistance.