Have you previously with your current Apple ID?
Confirm to download version 10.3.5 (or whichever is latest for your OS). Why Direct DMG Links are Rare garageband 1035 dmg link
GarageBand 10.3.5 represents a sweet spot in Apple's software compatibility timeline. It was one of the final versions to support older macOS operating systems while still offering modern features. Have you previously with your current Apple ID