This is usually because LoseIT doesn't have permission to write to Apple Health. To enable the LoseIT connection take the following steps.
Sign into Lose IT,
- Navigate to the Me tab on the bottom
- Navigate to “more” in the mid-line list of nav
- Navigate to Apps and Devices
- At the top of this page you should see “Sync Apple Health Data”
- Set Auto Logging to “on”
- Then enable read/Write food and nutrients.
Then that will give you the Apple Health Prompt to enable it.