I have X-Plane 10 with Boeing 777 Worldliner Pro- Extended Pack, which is designed to model the real-world operation of the 777.
Why does the AP never go to the heading hold direction even if I press the hold button?
Pressing the heading hold button will assume the current heading.
Pressing heading select will follow the course as selected in the display; this can be set by pressing the rotary encoder. It is also visible on the heading bug.
The Boeing 777 primary flight display will display
HDG SEL and
HDG HLD for each selection respectively.
"Heading Hold" is installed mostly for ATC purposes. Generally to insure horizontal separation between two aircraft. The pilot will receive that kind of message : "XXXXX...maintain present heading". It has not been designed to intercept the displayed heading.