Compatibility problems between After Effects and a Mac OS High Sierra computer.

I was working on some after effects files at on a more up to date computer. I have travelled to my second computer, an OS High Sierra. The After Effect files in the creative cloud are greyed out, plus I cannot find  an old download of AfterEffects. I was working on this computer a month ago. Some of the apps in the creative cloud are greyed out...not just after effects. I really can't afford to buy a new machine and what I am doing can be made to be quite simple. (ie I can work in older versions...)

I have work to do on it, and in the past this has been seemless.

Any suggestions as to how I can:

 1:Get a copy of After Effects that opens on this computer.

2:Carry on working on the files ( probably created in 23.1... but I'm not sure (as I can't open them!))

Thanks