Mr. Hide,
Your Mudmaster will NEVER calibrate in your current geographical location; because, you are beyond the farthest limit of the calibration tower in Mainflingen Germany. Which at its farthest range only cover the island of Sicily. Thus, you being down in Istanbul are well outside the antennas range signal. This is also the reason the calibration function is not coming on due to the module detecting that you are well outside the calibration range. But like I have said in my previous respond to you, it also could be that your Mudmaster might of been magnetized by a strong electromagnetic discharge which is generated by various electronic equipment within your house or place of employment.