Works just fine, like always. Verify whether your syncing works and completes (the circle around the device icon in GC Mobile closes and turns green). Also try syncing over USB with Garmin Express. Also check the respective subforum discussing your model of watch for possible issues with newly updated firmware versions - that's if you updated recently. If you did not, cnsider it.
Check out the forum for Vivosmart 3. Vivosmart owners are more concentrated there than here, so you have a better chance to get helped. Sounds like a device specific problem. Assuming HR graphs are complete for the night. If not, the problem may be in the HR detection.
