iTunes shows devices but is not syncing

Hi, first of all sorry for my bad english.

Since I've got an new computer I can't sync my iPhone5s/iPad4 anymore.

When I connect one of them via lightning iTunes shows the device and when I open the device in iTunes I can see all the installed apps correctly. But when I try to change something and click the apply button I can see the loading-circle for a second and the nothing happens.

This happens on iPhone and iPad so I think it's an iTunes problem. I tried to uninstall and reinstall iTunes but the problem is still the same.

I'm using Win7 (64bit) and iTunes 12.1.2. The mobile devices are using iOS8.3