Same problem here, no DA40NG menu in X-Plane 12 menu bar.
I used Plugin Manager to disable all plugins, reinstalled DA40NG and no change.
What does @Rando mean my "Moving" all third party plugins?
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Quick feedback. Running the .exe installer for Windows resulted in Avast! giving a virus warning and sandbox. Disabled the anti-virus block and re-ran the installer and the menu appeared.