Maybe the PT itrust board expects the interlock loop 4-17 to be closed ?
I had some weird funny shit with the pt itrust board as well, hence i threw it out.
Sometimes it started up in auto mode, and i wanted it to look at the ilda connection, which it didn't. Make sure to use a fully wired cable (so the interlock is seen as closed when the FB3 is connected on the other end).
This is what i can think of, there is also a keylock connection on the itrust, is that also closed ?
I didn't fail !
I just found out 10,000 ways that didn't work.