Just to be sure I understand and have the most correct information I will need to ask you some questions, and some may seem obvious but I'd rather not assume.
When you say, when I add a new person..., do you mean that you're just starting a new conversation, or do you mean you're adding them to your contacts when this happens?
If you're adding these people through your contacts app, do you get the same result if they call you? This cold mean that your contacts app is causing the silencing. Check the contact app's settings for anything related to silencing.
On that note check Google Messages' notification settings. Open GM>tap your profile pic>Message Settings>Notifications>verify allow Sound and vibration is active. I didn't find any other settings related to notifications in this app but look around for yourself to be sure none have been overlooked.
How are you starting these conversations? Do you open the app, and choose the bubble for new conversations, you open your contacts and choose the message option, you start dialing their number for the phone app or choose message from your call history, how are these started?
Something to try would be starting a new conversation with someone you already communicate with. I know many of us like to keep threads congruent maybe try starting a conversation with someone who has a second number you don't often use, or that has a second number that you don't mind deleting the previous conversation and restarting it. What is the result?
Another thing to try would be clearing the cache for the GM app. Settings>Apps>Google Messages>Storage>Clear app cache, you can also clear the app Data without fear of losing any messages according to Google's search AI.
AI Overview
No, clearing Google Messages data does not delete your messages. However, you will lose your Google Messages settings.
Let us know what you find for more help.
“do you mean that you're just starting a new conversation, or do you mean you're adding them to your contacts when this happens?”
When I add a new contact and have not set sound. Or first contact someone via GM. I have to set it. Once I set a sound, it always works.
Also, someone I have never contacted but are in my contacts, it doesn’t work… until I set it.
“Notifications>verify allow Sound and vibration is active”
It is active.
“How are you starting these conversations? Do you open the app, and choose the bubble for new conversations, you open your contacts and choose the message option, you start dialing their number for the phone app or choose message from your call history, how are these started?”
I don’t use bubble.
Most often I open GM .. and go to the chat I already have.
Sometimes, I open G Contacts, and hit Message.
A recent group messages, was new group. I had to set it.
Neither way, affects this.. both have no sound until I set it. Once set, always works.
“Something to try would be starting a new conversation with someone you already communicate with. I know many of us like to keep threads congruent maybe try starting a conversation with someone who has a second number you don't often use, or that has a second number that you don't mind deleting the previous conversation and restarting it. What is the result?”
I restarted a convo. I had sound set for them. It worked. It is not contacts that I have already set sounds for. It is any one I have never set sound. So I don’t hear message.
“Another thing to try would be clearing the cache for the GM app. Settings>Apps>Google Messages>Storage>Clear app cache, you can also clear the app Data without fear of losing any messages according to Google's search AI.”
I have done. I clear all of that once in a while for most apps
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