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Welcome to the Forums @Sevan09.
This might be happening because the P20 is not part of the supported devices list. This means that the app has not been fully optimized to work with that phone and thus things like this can happen.
As long as your phone fulfills the minimum requirements, Android 4.4 and Bluetooth 4.0, there is a possibility that it can sync but we cannot guarantee it. Some users have mentioned that following these steps with their unsupported phones has helped them with notifications, maybe that could help.
Let me know if you have any further questions.
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