No audible sound on notifications

I have tried everything possible but no sound comes through on notifications. I het a pop up and vibration only. I chose the notification sound on my phone and in the app. It worked. Then after one notification it stopped working. When i checked the name of tone i had chosen was replaced with the numbers 67981. Again i ticked the tone on my phone and app with the sound i wanted. It worked. Again after 1 notification it reverted back to the numbers. I have repeated a few times. Ridiculous. Should have kept my Blink cameras