As you said, it automatically accounts for interaction, because what the program does, is calculate the stresses at the predefined fibers, and then derive the forces.No need for input PMM interaction curves like in caltran section, different methodology.
What the fiber hinge is, is a finite...
Check simple things first. Assign mass as masses, not from loads and try again. Check internal forces in gravity analysis and check everything is ok. If not, vheck the hinge properties you assigned, especially yield. Even units could be wrong by confusion. Also check your accelerogram uits, some...
Pushover tutorial:
https://www.youtube.com/watch?v=CzqZVDse-eI
As for the fiber hinges, the maual covers pretty much everything, what exactly would you like to know?