Hi Dave.
Copy and Paste is for copying between similar data, not between scenes. You can copy the PEQ of one channel to the PEQ of other channels, or copy an Aux mix into other Aux mixes, for example as a starting point for creating monitors.

There is only one Main mix, so Copy has no function in this case. However, you can possibly do what you want using a different method:

Once you have set up your mix and want to put it into the scenes you have already created, you can update just the ‘Mixers’ item in the scene contents. To do this, touch the Edit button to open up the Scene Contents page. Open up the ‘Mixers’ tree in the right hand window. Touch the ‘Input Channel Mixer’ to highlight this item. Now touch Update in the middle of the screen. This will update just that item with the current settings. Do this for each scene.

Note that the ‘Input Channel Mixer’ contains all 64 channels of faders, mutes, aux sends, routing and DCA assignments. That means it updates your main mix as well as sends to the FX and monitors. The ability to update smaller parts of the ‘Input Mixer’, for example just the fader levels will become available in a future release of firmware.
I hope that helps,
Carey