If you have found that your customers are no longer receiving your shop's text messages, they may have opted out of receiving your messages.
This can be verified by looking at the customer's visit on the Active Customer Dashboard or on the Text Manager.
If the customer has opted out, they will only need to reply with the word "START" to your shop text number. If you need to locate your shop number, you can find it in the "Company Setup" page from the admin drop down menu. Once in the Company Setup page, you will find the text number under the "Business Text Number" section.