Wouldn’t any of the options work? Jesntyssy urnen. Jenti urnen. Jentī urnen.
I understand the conjugation is different, but I don’t understand how the other options are incorrect for this question.
Jentyssy is nominative plural. It doesn't work because the verb is in the first person singular, and "leader" in this case is an accusative object.
Jentī is accusative plural. It would mean "I see the leaders", not "I see the leader".