Thanks for the suggestion but if I’m not actively using Messages on my Mac, the app is closed. One of life’s mysteries.
I have been having this issue for a few years both for calls or for text messages. I seem to get a text message alert only whenever my phone is in the mood. I have to constantly look at my phone to see if I have text messages. I have never been able to solve this problem so if you are able to, please share your solution with me. I have tried all the usual methods (restart phone, hard reset, reset network settings) and all call screening is turned off. I’m on Verizon so judging from the other posts on this thread, this is not a carrier-specific issue. PS I do not allow Messages, Phone Calls or Facetime on my iPads or my Macs so that’s not the problem.
If the app is set to get notifications, they will come even if the app is closed.
Settings / Notifications / Messages. Make sure they are turned off. It would be interesting to see if that helps?
Sorry to hear this has been an issue for you for awhile, guess that means it’s not related to iOS 26. 
I agree, it seems as if it’s more if the phone is in the mood type of issue, that’s why it’s baffled me so much. If Settings are correct, the phone shouldn’t “decide” whether or not to ring. I’ve also tried everything you mentioned (phone restart, resetting network settings, etc) & have no call screenings set; nothing seems to help. I do allow Messages (not phone calls or Facetime) on my iPads & iMac but none of them are set to have an audible notification, only my phone is set to “ring.” And it apparently has a mind of its own as to whether or not it will ring. 
Yes, they’ll still come in but if the app is closed, the phone shouldn’t consider the message to have been read on the iMac or another device. I have tried that turning notifications off on my iMac but the problem persisted so I turned them back on, wasn’t worth the inconvenience if it didn’t solve the problem.
I very much appreciate all the replies & suggestions, happy to hear any others anyone has. Think I’ve figured out this is a problem w/o a solution. Maybe a future iOS update will correct it, maybe not.
I had much the same issue, and what solved it was replacing the phone (which was old, anyway).
I’ve considered replacing the phone but an iPhone 15 that functions perfectly except for the intermittent lack of ringing seems to be too new to replace. Given the minimal functional changes each year, replacing a phone every two years seems excessive and expensive. Keeping that thought on the back burner, haven’t ruled it out yet.
Thank you.
Yes, but it may think the notification has been heard.
I don’t like that behavior either - ring all the devices as far as I am concerned, watch, phone, tablet, and computer - but Apple’s design seems to be deliver the notification to the most obvious device, and if it thinks you’re using the Mac and the phone is locked, it may decide to push the notification there.
Until recently, my phone would ring and vibrate, my iMac would make an audible sound, AND my watch would vibrate, been that way for years. Each would also give a visual notification. Now, all will give a visual notification - I have to be actively looking at the device to see it - but the audible (ringing) & vibrations only occur sporadically. It’s frustrating but it appears I need to get used to it. Apparently things just don’t work the way they used to & there doesn’t seem to be a way to restore the previous functionality. Hope it will change in the future.
Ok, the watch.
From the beginning, either the watch will sound/vibrate, or the phone will, but never both - except for phone calls (and, I think, emergency notifications - amber alerts, government alerts, etc.) For messages and mail and almost every other notification it’s always been that way, from the beginning of the Apple Watch - it’s never both devices. If the phone is unlocked, it will sound/vibrate. If the phone is locked and the watch is on your wrist, the watch will. This is the major reason I haven’t been able to answer this before about message notifications - I always wear a watch, so my phone rarely vibrates with a message, and that’s the way it’s been since I bought my first watch in 2017, and I am certain
that it was this way since 2015.
See How to get notifications on your iPhone and Apple Watch - Apple Support
- If you use an Apple Watch, by default notifications go to either your Apple Watch or iPhone — not both. Choose where your notifications appear.
As for the rest, I’ve noticed this issue of the Mac delivering a notification (I have sound off on my Mac most of the time so I don’t know if it’s also making a sound) while the Mac is unlocked, and no other device making a sound, and that has been going on for years. It’s nothing new as far as my experience.
Thank you, I will read the article. I have been wearing the watch for years, all the time except for when sleeping. My experience has been very different than yours. Until recently, my phone rang (and vibrated) for all calls & messages AND my watch vibrated. For the last few weeks, it’s been haphazard for everything, sometimes nothing will ring or vibrate, sometimes 1 device will. Appreciate the link to the article, Apple has always told me my settings were fine & that notifications were possible on phone & watch simultaneously, maybe that has changed. I was told the easiest thing was to set up the phone to ring (obviously) and then set up the watch to Mirror My Phone. My watch has been set to mirror the phone’s behavior for notifications but to only vibrate (no sound). This is definitely a new behavior protocol for me.
I’m just here in a “misery loves company” capacity.
Half the time, the Mac doesn’t get the message for several minutes or even at all. (I’ll be waiting for an authentication number from a bank; the phone will get the text even though it’s asleep and the Mac will not even though it’s awake. iPhone SE 2nd generation, iOS 18 and earlier; MBA M3, macOS 15; no Watch.)
But back to the lack of ringing for calls, I’ve had that for years, too. I silence calls not from people in my Contacts, but there are entries in missed calls for numbers that are absolutely in my Contacts.
The authentication number phone calls/messages have recently become a problem as well. Sometimes neither the phone or the Mac get the message, sometimes one or the other will but w/o any audible notification. There have been times I’ve had to request the authentication number multiple times & maybe half hour later, will get the responses; they will all come in at once which is useless as each one negates the previous one so I never know which one will be accepted.
I’ve had this same issue in my iPhone 14 for over a year. My carrier is AT&T. It happens both to phone calls and text messages. For example, I’ll have my phone on my deft while logging into a site on my iMac. I’ll be sent a verification text and get no sound that the text has arrived. On occasions, calls come in with no ring. The phone is on the table of in my pocket. I don’t even get a missed call banner.
I’d been planning to ask this group about it, so I’m really happy someone has. , I’ve checked settings many times including Focus.
I’ve just upgraded to an iPhone 17. I’ll see if the issues continue.