I was seeing this when running my app on macOS 11; so for older versions, I added the menu option manually to get the keyboard shortcut working as expected.
On your WindowGroup in your App file:
.commands {
CommandGroup(after: CommandGroupPlacement.textEditing) { // place the new command after existing text editing commands
if ProcessInfo().operatingSystemVersion.majorVersion < 12 { // only add for specific versions
Button {
NSApplication.shared.orderFrontCharacterPalette(nil) // to open the emoji popover
} label: {
Text("Emoji & Symbols") // match what is added automatically on newer versions
}
.keyboardShortcut(.space, modifiers: [.control, .command]) // match what is added automatically on newer versions
}
}
}