Lifestyle tracking notifications not working

In the Connect app go More -> Settings -> Phone Permissions. Alarms & Permissions should be at the bottom.

I have fixed it on mine.

I uninstalled and reinstalled Garmin Connect, which then allowed me to reset permissions from fresh. Then I started receiving notifications.

HOWEVER. If I forget to log for too long, and/or clear the notification without logging anything, it stops the reminders. At this point, changing the time of the notification gets it going again.

Exactly this. Reminders work for a while and then... they don't. I have to regularly (like 2-3 times per week) go into Lifestyle Logging, change the reminder times, and then it starts working again. For a few days at least.

Same for me - if reminders stop, changing the time triggers them anew. Last week reminders have been on schedule though

So for me, the solution was with Android. The Garming Connect app did not have the permission to set alarms in my Android Settings. It wasn't there at all. I have a Pixel phone and apparently, I had a security update which I had to download and install. After that, the permission to set alarams returned in the permissions screen, I turned it on and it started working again. 

You could try and force your phone to search for updates and install them if they are there. Might help. Or I am just lucky.