For this issue when you change channels on your Android device, we recommend to reinstall the application on your phone, since you already know that the Slingbox is working good because you can change the channels using Watch at slingbox.com.
I am having the same problem also. The app will change channels by swiping up or down but not using the keypad. Obviously the ir blasters are working and positioned right. Same behavior on both the Android app as well as the iPad & iPhone apps so it is not app specific. Channel changes fine when watching on the pc using "internet viewing". I did the uninstall, reboot, reinstall on all devices and it makes no difference. Also re-ran the setup function on the slingbox itself as well as unplugging the slingbox. Makes NO sense what so ever! VERY FRUSTRATING!