645M Message notifications not working

Notifications for text messages and from hangouts didn't work for me when I first got the unit but did after it updated itself to 2.4 and we're now on 2.5. So making sure your firmware is up to date is the best I've got.

I'm using an Android device but it's running LineageOS rather than Samsung's stuff but on my phones to bring up the android permission settings, like what the calendar prompt would have been I can long press the app icon then drag it to the info icon at the top of the screen and select "Permissions". Going to "Apps & notifications" under settings and then selecting the Connect app will also take me to the same info screen.

Sounds like you've already done this next part but for completeness with everything I can think of. In the connect from the connect app "Settings" from the main menu, then "Smart Notifications" making sure the app(s) you want are toggled on or really for testing purposes I'd suggest you turn on "All Applications" and see what happens.

Played with all those settings. Still nothing. I've even started using a third party message service, just to see if that worked. It didn't. This is so frustrating, I should love this watch, but right now I hate it.

If you have updated to the most recent 4.5 version and have confirmed that all of the SMS permissions are enabled in the Garmin Connect Mobile app, we would encourage you to reach out to our Product Support team. This will allow the team to collect more specific phone information and App Diagnostic information so that this can be investigated further.

Same here, This watch is perfect, look, size, weight, functionalities. But I start to hate it because of those notification not working.
Opened a case with support, send all the data requested, but still not having the answer.

In my situation, it worked for few hours after I unbox it, but as soon as the firmware updated to 2.40 (now at 2.50), no more notification.
Phone notification are working, and calendar sync perfectly, but no notification for the others.

I thought I got a couple of phone notifications when I unboxed the watch (security codes as I set it up), then upgraded the firmware and haven't received any since. Does anyone know if there is a way to roll back to an old firmware version and test?

I had a similar issue. I got most notifications but not texts or calls. In my Android, I went to Settings --> Apps & notifications --> Connect (The Garmin app). Some permissions were on, but phone and SMS were turned off. When I turned them on, problem was solved. I thought I gave the permissions on the front end, but either I didn't or they got changed. Android was blocking them. It was not on the Garmin side.

I also experience problems with SMS( text) Messages 645M, I would receive notifications of a new Message but could not read the actual text content, tried every setting commonly suggested,
Eventually I found that Preview Message has to be switched ON, on the Phone :Samsung A8 Andriod ver 8.0.0

Phone settings >Notifications>Messages App>more settings(In-app notifications settings).Preview messages( show previews of new messages on the lock screen and in pop-ups) switch ON

Thank you for this!! I'm using ios and just spent 2 days trying to figure out why I was getting phone calls, social media notifications etc but no messages. 

I don't like having previews on my phone so its like... do I want my watch to get notifications or my phone how i want it!

Thank you, again!