Ok first things first, have you used a Fike Twinflex panel with the correct Fike devices? Twinflex is a beast in its self and as such you need to use the correct devices with the correct panel
Secondly, you say you connected the EOL as you went along? What do you mean? do you mean you installed device 1 on zone with EOL, fine. Moved to device two with EOL, fine and so on?
Have you checked all bases are fine and wired correctly? Haven't crossed a pos and neg in one base?
Edit: Also, have you swapped zones around in the panel to prove the fault is with the panel or field wiring? and also, if it is a Fike system, there are no EOLs. The EOL is built into every device and i think you indicate the last device by switching a DIL switch on the back. Sorry, its been so long since I've worked on anything Fike. Most people in the fire industry avoid it like the plague as its crap and known as an electricians wholesalers special! (awaits flaming lol)