Trunk will not open from inside or outside.

Key was inserted but it will not turn counter clockwise as manual states. In fact, key will not turn at all.

you have to use the master key,not the valet key.if you are sure that you are using the master key,then there is another way,maybe to unlock it.

Master key would not easily go into the lock. The factory spare key went in without problem but doesn't turn in either direction. What is the other means to unlock the trunk, please.

try this way. just remove the lower trim piece that has 3 philips head screws, remove the clip-in panel to the left of the steering wheel to reveal another philips head screw, remove that screw and pull the panel down to where you have access to the locking cylinder in between the gas and trunk release. You will see a small metal band incircling the lock cylinder, move that to the left to reveal a small black button that is pressed, get a screwdriver and press it and it will retract and the cylinder is unlocked and your trunk release should work! let me know if this works.