If MondoPad v3 is already installed and not working properly, try repairing (Modify) Mondopad Client application.
You can access Mondopad Client application from, Settings ⇾ Apps ⇾ Apps & features.

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Failing that, uninstall and reinstall Mondopad v3.
When uninstalling, make sure to delete all programs that mention MondoPad and SQL.
Then,