It's been several days, why is this not fixed yet?
If you have an Android and are using the Messages + app, if you go back to the regular Messaging app and set as default Messaging app, and change the smart notifications in the Garmin Connect app to get notifications from Messaging app (the yellow one) and unclick the Message + app (the red one), the text messages will start showing up again on your device. Easy fix for those who have androids and text notifications aren't working on device since software upgrade. I just fixed mine! Yay!