i need help backwards compatibility for halo wars

I have the digital copy of halo wars and want to transfer it over to my xbox 1. but it isn’t coming up for “ready to install”. I search it on the game store and its telling me to rebuy it… its -Yoink!- me off tbh lol I already talked to xbox support and they confirmed that I have the license for halo wars(which is confirmed that I have bought it before)but its still not letting me… HELP