This helped me to make it work on an Android.
https://www.youtube.com/watch?v=YSOOAxxceJ4
I upgraded from a Vivosport to the Vivoactive 3 & texts weren't coming through. Checked all permissions, everything looked good, but no texts. Uninstalled Garmin Connect app & reinstalled. Synched with watch, granted all permission when prompted & everything working now. If you were already using the app with a different device before adding a Vivioactive 3, you might want to try this.
If you have an iPhone. Toggle Allow Notification on your iMessage setting under Notifications. If that doesn't work, Check if your phone is on silent mode. Also toggle Notification Settings on your watch. Works fine for me after. Hope that helps
Thank You! I always forget that within the App on your device (iPhone or Android) there are permissions for the individual Apps in settings. Great reminder and worked immediately! Thanks for the post!!