Here at work all our workstations were upgraded to CC when that came out. Then CC2014 when THAT came out. Since then we've added a new workstation and it seems we can only install CC2014 on it and not the early CC version. We work with many versions on a daily basis (everything from CS3 to CC2014), so we need CC on this workstation as well. But when we go into the Creative Cloud panel it's simply not available.
Go to the Creative Cloud Desktop app. Click on the Apps tab. Scroll down until you see Filters & Versions (or All Apps) on the right. From the menu choose Previous Version.
Aha! Thanks, Steve! Not very obvious.