No sleep data Forerunner 55

First question, did you do a soft reset after the update?

I didn't do anything; the update finished and the phone appeared to work as it did before the update.

By "soft reset" do you mean switch it off and back on again?

No. You need to hold the backlight button until the watch turns off. After the screen goes dark, press the backlight button again. Look at the videos on YouTube.