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Have you tried going in to Settings, My Lines, then go under Ringtones. (You'll also want to make sure the line is Active in the app.)
Give that a shot and let me know if that works.
I am using a Blackberry DTEK60 and my phone rings with headset plugged in or not. But it doesn't ring with bluetooth headset paired.
Found this thread as I am having similar issue on iPhone 7. When I follow the above solution of checking my ringtones, the options are grayed out and the info at top says "Custom line rigntones are played when the DIGITS app is using Data only" but when I do "data only" setting I go off-line repeatedly when in my car or driving around so do not receive texts or even the voicemail/missed call.