I would have thought that if you opened the SimIcons panel (SHIFT+2) then click on CL (Cargo Loader (top row 3rd from the left)) that you would be able to open the large cargo door within the Cargo Loader panel. But.. Having tried that, the Cargo Loader isn't opening for me, so I too can't get the main/large cargo door open.
I tried clicking on all the words that had "Cargo Door" written in them on the Animations Panel (SHIFT+3), but none of those opened it either.

So it looks to me like there is a problem when it comes to opening the main/large cargo door on the Captain Sim B767-300CF.


Note. I had a look at the panel.cfg for the CS_B767-300CF-II_CF6-80C2:

[fltsim]
alias=CS_B767-300ER-II_CF6-80C2\panel

which, as you can see, aliases to (points to) the CS_B767-300ER-II_CF6-80C2 panel.cfg, and in that panel.cfg I can't find the Cargo Loader "window" anywhere (which would explain why when clicking on CL nothing happens).  :(