I thought my app had stopped logging to the logcat (activate by Alt+6). For some reason the filter was set to by package. There did not appear to be any error in this. But Android Studio wasn’t showing me any entries against my package. Maybe this is a bug, cause it only started happening when I upgraded Andorid Studio. However, when I changed the filter setting I saw my log in logcat again. So try changing the filter.
Log.d Seem Not to Add To The Log (Logcat)