What is the reason I can not copy clips from PP to AE? I have reinstalled both, changing the order in which I install them. Any ideas?

I have never attempted to do this and I dont think it is possible.

You can export clips from premiere pro, then import into after effects, and then import the after effects project directly into Premiere and choose what composition(s) you want
You can import a premiere project into after effects and then edit if you wish
You can import after effects projects directly into Premiere
You can use dynamic link (I have never used this so read the manual on how to do it)