yeah, they found that the Bixby app was causing this weird bug, but if you update the app, it should fix the notifications bug. They released the update notes and it says it was causing no notification sounds for some apps...
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I'm still on the sprint network and I'm having the same issue for the last 3 days. no notification sound when I receive a text message. samsung tech expert got it working this morning, but after the first text. my note 10 + went back to no notification sound when receiving a text.