I tried all and finally found one solution googling: 1) In the Handset, press Menu 2) Then press *7890# 3) Press Down until find Test Handset, then press Select 4) Press Down until find Register Clear, then press Select. 5) Will ask if you want to Clear, Select Yes. 6) After some seconds it will put OK in the screen. 7) You will need to register the Handset again using to right method in the manual. And that's all. And now My Vtech CS6929 it's working great!