Cakewalk UA 25EX optical Out to Edirol MA 15D optical In ?

Hello !
 
My first post here:
 
I have Cakewalk UA 25EX connected to Edirol MA 15D monitors via optical cable
Cakewalk UA 25EX optical Out > Edirol MA 15D optical In.
I allso have guitar connected to Cakewalk UA 25EX Input 2 via 1/4 cable.
Problem is that I only hear signal from my PC and not from my guitar.
( When I use headphones - I hear both of them - PC and guitar )
Can someone please help me out here ?
 
All Best,
Omrat