First check if you haven't accidentally put the spell on ignore (see 'how to hide spells' FAQ).

If that's not the case it probably means that I haven't gotten around to register your spell in the class modules. At this point you can only ask me to add it using a Feature Request here on my portal.

However, the current version of ForteXorcist does support adding 'unknown' buffs and debuffs at the Spell Timer and Cooldown Timer. You can type the name of the missing buff/debuff at 'Customize', and select 'show' for it.

Note that the Spell and Cooldown timers support different types of spells and different types of units, so what you want may not always be possible (yet).