Chanting the enn will get the spirits attention, but it is more of an invitation than a summoning, from my understanding, so the spirit may or may not show up. Demonolatry, from which enns originate, is a religious practice, and doesn’t believe in commanding a demon to appear.
In my opinion, you will get the same result if you open a seal and just chant, “Sitri, come.”
If you want to summon the spirit, instead of using the enn, I recommend EA’s Incantation to Summon Forth: