SAOs are displayed when:

• their activation condition is triggered
• they are already here and the player logs out and logs back in

However, SAOs are not displayed when:

• they are already here and the player runs a "reload UI"

This is due to the fact that the game client sends SPELL_AURA_APPLIED in the two former cases and not in the latter.

Suggestion: check if a buff is present when registering it through SAO.RegisterAura of shortly after all registrations.