In October 2018, the Google Play Store announced that they would restrict the use of high risk or sensitive permissions, including the SEND_SMS permission that ODK Collect uses for automated/background sending of submissions over SMS.
Over the last few months, we have spoken with our contacts at Google to see if Collect could be provided an exception given the humanitarian nature of our work. Despite much back and forth, an exception has not been granted.
If we continue to use SEND_SMS, Collect will be removed from the Play Store. A removal would be a catastrophe for every user and, for that reason, Collect v1.20 and later will disable the SMS sending feature until we can find a viable way forward.
We know this change will make it very difficult for users who rely on SMS to transfer data in places with no Internet connection. If you need to use SMS, your best option is to not upgrade (or download the APK). You can also continue to send SMS during a form filling session through specifying a URI as intent data.