The bare minimum of info needs to be entered in the PVR Client NFPS settings so there's very little that can go wrong:
Active Portal: Either NFPS, IPTV Rocket or IPTV66 (Depending on your donation)
MAC Address (last three hex groups only): Self explanitory XX:XX:XX
Time Zone: You've already entered this
Donation: Your donation/route/rocket number
XMLTV File: Your choice either English Only or All
Connection Timeout: 120
If, after disabling 'Hide No Information Labels' you don't at least see channel names then disable Live TV, disable PVR Stalker Client NFPS, clear data in tv general settings, clear data tv guide settings. Exit Kodi. If possible on whatever device (e.g. android box, firestick etc you're using clear Kodi cache in app settings (if you can't just skip this step). Link a fresh MAC to your donation. Launch Kodi, update PVR Client settings with last six digits of your new MAC address in the format XX:XX:XX & make sure you have the other fields filled in with info as above. Enable PVR Stalker Client NFPS, enable Live TV.