You can’t import them in Bins first ‘before’ you convert them to ProRes.
They are dropping because you can’t edit with these files in FCP/
Now you have the original H264 versions in your project. Which you DON’T want.
Convert them to ProRes using
a. Compressor ( already on your mac)
b. Mpeg Streamclip
c. Log and transfer 7d plugin.
You can always download the plugin or mpeg streamclip on your home computer.
Put it on a USB stick and then install on your editing station.
Also.
Search these forums for 5D/7D workflows in fcp