same happened to me. I have iphone 7 plus and fenix 6s sapphire. i called garmin support and walked through everything. Apparently it’s an issue with the iq app connection to your watch. Workaround solution…
Are sure you have the latest firmware installed on the watch?
Try rebooting the watch. Hold the upper left button for 15-20 seconds until the watch turns itself off, and then turn it back on.
Having the same issue today and just bout the watch, not impressed....