Age of Empires II (2013)

Age of Empires II (2013)

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New Units
Hi. I tried to install the Relics of Athalen mod from Heaven and I made it.
There's only one final step to make it work: find a way to make the scenario accept the new units that come with the mod. Whenever I click on the campaign and then on the first scenario (The Secrets of the Old Kingdom) it tells me: "Attempt to acces invalid units. This world allows the following packages: Age of Empires II (Original Game), The Conquerors (Original Game)."
Please, could you help me figure it out how to make it to succesfully acces the new units?