> I am 100% positive that I was able to copy multiple keyframes or duplicate them just by holding down the alt key and dragging
That has never been a feature of After Effects.
> hitting cmd+c and cmd+v
I just tried copying and pasting multiple keyframes using these commands, and it worked fine for me.
> I really don't understand why adobe would disable such a helpful feature,
We changed nothing in this area.
duplicate them just by holding down the alt key and dragging
That's nonsense. Holding down the Alt key stretches/ compresses keyframe spacing, i.e. changes the relative timing of a group of selected keyframes.
Thanks for your answer but I still can't copy the keyframes by using cmd+c and cmd+v nor by using the edit menu. Are there any settings for copy-paste or something? When I select the keyframes they become yellow as they should but then I copy and the only thing pasted are the layers. Any other suggestions? plugins missing? anything???
Are you selecting multiple keyframes on multiple layers? If so, that is not going to work. Try selecting and copying multiple keyframes on a single layer.
I tried to do both and you are right it doesn't work on multiple layers (strongly recommend it for the future versions), but it doesn't always work on a single layer especially when I am using the shortcuts, sometimes it doesn't copy and paste and I hear that sound like it's unable to perform that action. It's not a hardware issue because I am working all day long in Illustrator, Indesign etc and everything works fine with the shortcuts.