Cant update GarageBand to older version MAC 10.13.6

Recentely had to perform a complete restore for my MAC. From back up. The back up was a little older, so the garageband version is old and wont open my existing projects. So when I try to update the garageband to an older version, a pop window keeps coming up, saying download. Click Download and it just reappears again.

I've tried updating from my recent purchases and have performed an update on my MAC to 10.13.6, Adn a restart.

Would love help