I would like to post any data on steps, weight, heart rate, and active energy to notion, but it is not working.
You have not provided any details about what exactly about what is not working in what you have, what you have tried so far, or indeed what you currently have in place that is causing you the issue. As a result, it is impossible to advise on what is going on there and how you might resolve it.
More generally, access to health data is built into Shortcuts (though there are also permissions in Settings > Health > Data Access and Devices > Shortcuts to be mindful of), and if you have not already, it may well be worth your while looking at Nautomate for your access too Notion.
Hope that helps.