Same happened to my ICD4 just last week. On the same windows PC, the ICD4 works fine with the latest programmer (IPE 5.50?) but is not working with MPLABX 5.50. I went back to MPLABX 5.45, and then all worked fine. After that, tried the latest MPLABX again, and it also worked. But not very well. Hanging regularly. So for now I stopped using the latest MPLABX (5.50?).