777 autopilot disconnect caution

[avi8tir 24]

If I am on approach or after autoland and I turn off the autopilot, the master caution goes off and wont stop even after attempting silence the master caution. only way to shut it up is to turn autopilot on again. 

What am I doing wrong?

[B777ER 2,475]

Setting in the FMC silences it when you click the master caution. Seek and you shall find in the options.

[spesimen 135]

from page 49 of the introduction manual:
You need to press the autopilot disconnect button on your joystick (or the Z key) twice in order to silence the alarm. Make the first press, wait a second or two and then press it again. If you double-press too fast, it won’t silence. Always use the disconnect button, don’t use the disconnect “bar” on the MCP – you’ll have the siren constantly going off if you do.
On aircraft with the RESETTABLE SIREN option set to NO, pressing the master warning button on the glareshield will not stop the alarm – this goes for any master warning in fact, not just the autopilot.

cheers,-andy crosby