Do you have a specific design you are talking about? Can you post a link in the forum?
As far as troubleshooting, the HR sensor polls once every 15 min. It tries to take a reading for 30 seconds. If it cannot get a value, then it will read zero. Initially when the feature was released, there were some issues with the tag on Huawei, but that was resolved with an update. See below.
My guess is that the Huawei Classic doesn't have a very good HR sensor and has a difficult time getting a reading when moving.