No, Smart IPTV application does not include any channels and no information will be provided about where you can get channels or channel packages. Also, application developers are not responsible for the content uploaded to Smart IPTV.
Each TV has 2 MAC addresses (1st is WiFi, 2nd is Ethernet) and a 2nd MAC is activated automatically after you switch to another connection type and restart the app. MAC address is unique for every TV and cannot be changed manually.
Turn your TV off from power outlet (cord) for ~1 minute to clear the cache and then try again.
Try example test list http://siptv.app/lists/example.m3u (external URL) first, then then check your playlist for errors. Make sure your URL is a direct link, not a redirect and that it is currently online. You can also try downloading your playlist file by putting the playlist URL in the internet browser address field and use it as a static playlist at My list page.
In case of Check playlist URL you can try turning off your TV/device from power for ~1 minute to clear device cache.
Additionally, try reducing your playlist size by removing channels/movies (especially if you have LM series LG TV with limited memory). If your playlist doesn't appear on TV or disappears after restart, try checking Save online box, when uploading the playlist. You can also try resetting Smart HUB or turn your TV off and on to clear the TV cache if you have Samsung TV.
TVs have limited memory available for app storage, so if your playlist is too big (~5 Mb), it will fail to save in TV's memory.
Try example test list http://siptv.app/lists/example.m3u first, then make sure all your stream links work (not dead) and codecs are supported by your TV. Every TV make and model are totally different and may or may not support specific stream formats:
If you have LG webOS TV, you can also try changing Stream Player Type to NC Auto in application settings.