When I select multiple units of different types my commands on the UI disappear but if it all the same unit if fine and able to command. Zenotheory
i noticed something similar when i tried to let a group of mixed construction units build something. as soon as the selection of units stops being homogeneous, the command-bars vanish and all you can do is move them.
i know, but i kind of have been proven to be rather bad at finding things. almost all of my reports have been closed down as duplicates.
Then try searching more terms and synonyms for the words you're using. If you're bad at searching the best way to help is to get better at searching... not move stuff over to the forums.