Locked screen text audible notification

[45nhfarmer]

I am using Message+ with my Turbo 2.  My notifications for Message+ are set to ring and vibrate, along with the pop-up window for new texts.  If the phone is unlocked, all is fine.  If the screen is locked, the phone vibrates and the pop-up window shows, but no ringing to alert of the new message.  In the Do Not Disturb settings, Message+ is set as a priority, however, I keep the Do Not Disturb in the OFF mode, and do not use it.  Am I missing a setting to allow the ringing when a text comes and the screen is locked?  I think I have checked EVERY setting that I can find!  Thanks.