1. Give it time
The guide loads after the channels. On first setup, wait 5 minutes.
2. Update the guide
Settings, TV guide, Update TV guide.
3. Use Xtream Codes
Playlists added as M3U links sometimes load channels but no guide. Remove the playlist and add it again with Xtream Codes.
4. Add an EPG source
Settings, TV guide, EPG sources, add the guide link your provider gives you. LemonRealm customers can ask support for it.
5. Wrong times?
Set the device time zone to automatic. In TiviMate, leave TV guide time shift at 0 unless times are still off.