Sometimes it might happen that your Watch Face is not updating on watchOS 10 as displayed in the picture below. However, this can be fixed easily.
First of all, please ensure that your Apple Watch and your main device are on the latest version.
Usually, deleting the Complication and re-adding it resolves the problem. If this does not work, you could try a different Watch Face.
The Complication still doesn’t update
If this doesn’t work, please try to check off one of your tasks on your iPhone. This should trigger an update on your Apple Watch.
Alternatively, you can try to edit one of your current tasks on the widget and see if the Complication is updating now.
Finally, you could try to restart your Apple Watch.