Hello @pete-67.
At this moment the Galaxy S9 is not on the supported devices list. Our team is aware of the need to expand the list and as soon as we have any news on the matter we will be sure to let everyone know.
Keep in mind that while the app can work as long as the phone meets the minimum requirements, Android 4.4+ and Bluetooth 4.0, there is a possibility that some issues will happen. Some users of phones not on that list have mentioned that going through these troubleshooting steps helped them, so it's definitely worth a try.
Let me know if you have any further questions.
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