Not sure what you're working on in order to remove the coils, but just in case you weren't removing your spark plugs also, check to be sure you haven't spun the little screw on caps off the spark plugs.
You'll need those back on the plugs, and also be very careful to locate them if you are removing the plugs so they don't end up along side the plugs before removal, and in the cylinder afterwards....
Theyre likely to get stuck in the coil where it snaps onto the plug, but just in case....!