There is a known issue with Apple's iOS 14 update where your Apple Watch is dropping health sensor readings from the automatic Health synch to iPhone. It will appear as though you were not wearing the Watch for extended periods of time when you actually were. If affects all Health & Fitness apps that read Health data from iPhone.
Other symptoms include the iPhone heating up, reduced battery life, periods where the iPhone does not respond to touch, missing workouts and lost GPS history. This seems to be affecting around 10% of people that did the iOS 14 update.
There is an Apple community discussion on this here.
And a very big one here.
We setup up a help page here that you can refer to for additional information.
Please visit our FAQ page for any other questions. It contains 95% of answers to support questions here. We've looked through thousands of support emails and these are easily the most common ones all answered.
Contact Us via the iPhone App
We highly recommend sending any support from the link within the HeartWatch app, as it will send us a little bit of extra information to try and diagnose the issue, such as your current iOS version, WatchOS and so on. It is found in Settings (the little cog in the top right corner) and then tapping the Support link. See below: