Hi, i suppose u are talking about the windows version.
0) It turns to 0:00 when the entered time has a wrong format.
Go to Windows Regional Settings and look at the Time Format. Are you using the correct time format when you enter it in MLO?
1) Maybe you are using a foreign language keyboard. Choose English layout (language) and try to enter time again.
2) Every standard keyboard has 2 number pads. One is above the letters, and the second is to the right of the letters.
Test both of them, maybe one of them will work.
3) restart the PC. Close all running apps. Try again to enter time in MLO. Maybe some of them are interfering with the numpad keys.
4) Is NumLock active? If not, then press it.
Best wishes
Andrew, MLO user