I’m having a similar issue, I’ve been searching through all the threads I can find. This is my situation:
I have a Garmin watch constantly connected through Bluetooth to an iPhone 14 Pro Max. I’ve checked focus, the side switch, contacts are not muted, notification settings (endlessly), etc. I actually even did a factory reset, and started from a blank slate. I also have a MacBook Pro and iPad Pro that I forward messages to through my iPhone settings. I’m not sure if this is part of it or not, but it doesn't seem to be.
I also understand that the default behavior is for the phone to pass the notification to the smartwatch if you have one, which I do, even though it's not an Apple Watch.
I’ve only been testing iMessage by sending myself text messages from Google Voice, and asking one of my contacts, John, to text me.
Google Voice iMessage Test:
Bluetooth on, screen locked. No sound on iPhone, watch vibrates.
Bluetooth on screen unlocked: Sound on iPhone, watch vibrates.
Bluetooth off screen locked: Sound on iPhone, nothing on watch
Bluetooth off screen unlocked: Sound on iPhone, nothing on watch
All of those seem to make sense based on the design, however…
Test with John:
Bluetooth on, screen locked. Sound on iPhone, watch vibrates.
Honestly, this is the behavior I want, but what's driving me crazy is that it’s not consistent, I can’t figure out why John’s messages make a notification sound, but my google voice texts to myself do not. I've checked the settings on the contact card, and I don't see anything different. I also checked the conversation itself in iMessage, and it looks the same.
What's even stranger, is that every once in while the Google Voice texts I send to myself will make a sound on my iPhone and vibrate my watch, but I can't find a pattern to this one. It's very infrequent and seems random.
Also, other apps seem to make a sound and vibrate my watch. For instance, I use Outlook for work, it makes a sound on my phone and vibrates my watch every time as long as I don't have a do not disturb set.
If it's the design that the phone passes the notification to a smartwatch, I guess that makes sense, and I can try to live with that. But being on Garmin, I don't think I have the same notification options on my watch. But I prefer the Garmin watch because I use a Garmin head unit for cycling that connects to sensors on my bike. So I'm already in that ecosystem, and I like the training metrics.
Even still the fact that it's not consistent is really bothering me.