I'll summarize the steps necessary to not have the authorization fail. You need to have a current donation/rocket/route... if you got a MAC only from a reseller, go to back to that person for support.
1. Go to the donation checker for the service that you have and modify your current MAC. Your first 6 digits are 00:1A:78, and modify one or two of the last six digits and save. If it doesn't take, try a different MAC.
2. In Kodi, go to File Manager, select Profile directory, addon_data, plugin.video.stalker and delete settings.xml
3. Go to the settings for IPTV Stalker, and enter the new mac in your appropriate portal. Those who are got this addon automatically were using the iVue repo, so you will also need to put the mac in Portal 1.
That should be it. If you still get the error, repeat steps 1 and 3. You should also be able to use the new MAC in PVR Stalker, the STB Emu and the Official Android Emulator. If you have a MAG, you shouldn't be using its MAC on the Kodi apps, because you can't change it, however, if you can make it work, good for you!