SwiftUI App works fine in simulator, but not in preview-CodePudding

I'm trying to get preview working in Xcode. Just a simple test app written in Swift. Grabs rows from a Realm database and lists them.

It works fine when I build/run in the simulator but none of the data shows in the ContentView_Preview.

App in Simulator App in Preview

Here's the code:

import SwiftUI
import RealmSwift

struct HeaderView: View {
    var body: some View {
        HStack(alignment: .firstTextBaseline) {
            Text("Time Spent").font(.largeTitle)
            Text("or waisted...").font(.headline)
        }
    }
}

struct GroupListView: View {
    @ObservedResults(TaskGroup.self) var taskGroups
    var body: some View {
        NavigationView {
            // Nothing from here shows in the preview.. but shows fine in the simulator
            List(taskGroups) {
                Text("Group: "   $0.name)
            }
            .navigationTitle("Task Groups (\(taskGroups.count))")
            // Grrr
        }
    }
}

struct FooterView: View {
    var body: some View {
        HStack {
            Text("