For those who are using IPTV Stalker as the server for the simple client, make sure that you can get channels from that first. If you can't, and have checked your settings (Correct server url, and MAC, using 00:1A:79:xx:xx:xx, where x is a hex-digit (0-9, A-F), and the server is on), clear the cache by going into the context menu where you see NFPS (menu button, "c", or right click).
If you are not on Kodi (14.0 and greater), the IPTV Stalker shouldn't work. Also, if you are still having trouble with channels, always try resetting the PVR and guide/EPG, and disabling/enabling Live TV. Also, remember that this server is in test mode. That means that its common that your favorite channel may not be up when you want it the most (i.e. right now). If you are seeing other channels, that just means that current channel may not be up. If its global, do a little reading to see if others are having issues, especially those who have yellow or blue letters for their usernames.
Those who can, upgrade to Kodi 15.0 beta, and see if PVR.Stalker (0.8) is better for you. Upgrading to 15.0 may not be the right thing if you aren't secure in your Kodi skills and can't bear that a favorite add-on no longer works.