How to avoid the fail of LMS adaptive filtering?

Hi every one .... I have a project that uses LMS adaptive filter to extract fetal ECG from an abdomen of a pregnant mother according to her chest signal.I used DaISy database but the adaptive filter did not produce the correctly expected error signal.What measures should be taken to adjust the operation of the adaptfilt.lms..... maybe in terms of step size of number of taps or something else ?

What do you mean by "fail"? Not converging?