Maybe this will help.... first part.... the remote must communicate with the tiu else nothing works period...Hit the "read" bottom left on the remote and we should get the Message TIU found with no aiu box connected or something very similar, The important part is tiu found. Give it a try,
Second part The tiu need a power supply to turn on (function operate). Power to fixed 1 or an aux power or both works . I noticed you tried fixed 2 but fixed 2 is a straight through connection which will allow voltage through but unless the tiu is turned on there will be no dcs signal so thinks don't work.
The red out put from the tiu channel must go to the center rail.... try it again....good luck.
