This is just a guess, but what you're describing sounds familiar. I have a different brand of camera and a Samsung phone and I get the same thing - a notification pops up on my phone, but there's no audio alert. Oddly, it triggers the alert on my smart watch (non-Samsung) and the smart watch gives me an audio alert. I think it's something with the phone, but I haven't delved into what the problem could be.
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