Not all ligatures work?


I’m loving Fontself for its ease of use, but i’m encountering some problems: not all ligatures work.

Now, I don’t know how OTF fonts technically work with UniCode and stuff, but here’s my problem:
I’ve created the it / itt / fitt / ffitt ligatures for my font (see picture) and in the Fontself preview they work just fine. Once the font is exported and installed, Illustrator just uses standard ligatures while the “non common” one i added, not.

I hope someone can help.

Thank you!