I finally gave in and contacted Apple Support today. I linked their Chat Support to this Discussion page but they were still unable to provide any answers so they put me through to Telephone Support. After 14 minutes of re-explaining the situation to TS, they offered to ScreenShare with my phone to see my settings. When they were unable to send the invite, they asked to call me back in three-four minutes to continue. I agreed. After waiting ten minutes, I got back to Chat Support and asked them what happened. I was promptly called by TS only for the line to die when I was put through to a person after the operator. I went back to CS and they said they were trying to get a phone call through and kept setting up call backs which I never received. They gave me numbers to call which were not connected. They asked me to call the numbers I had been contacted on and when I did they had recorded messages saying Technical Support was closed and to call during office hours. They asked me to call a friend to see if I had signal - which I did successfully. They asked me to turn my phone off and on again. After 129 minutes of waiting for a call back, they suggested scheduling one for 9am tomorrow. Once they eventually got the right 9am time zone, I let it drop. Apparently there is no record of sound notifications not working and for some reason Apple is not functionally aware of this Discussion Page on their forums. So I recommend that as many of us that are patient enough contact Apple Support and ask them why our phones aren’t working properly because apparently they’re unaware of it being a bigger issue than just my device. I will report back tomorrow after my phone call with them if it happens. Turning off Bluetooth does work, however I cannot lose that functionality. Besides which, the phone worked properly for us all before, why should we have to miss out on a substantial feature due to a glitch in their programming?

Apple Telephone Support didn’t call at the organised 9am time. The called at 9:30am. we spoke and troubleshooted until 11am but were unable to find any solutions or causes for the lack of sound notifications on the Lock Screen other than turning off Bluetooth. I now have appointments, so they are going to call me back tomorrow at 9am to continue troubleshooting. unfortunately it was difficult to test things as I only have one phone and to get the phone to lock whilst in a phone call is impossible. outcome: solution and cause still not identified.