I have Trueflow 3 v. 4 and use Flatworker to make Impositions. When I view the preview in Trueflow the marks I placed in the gutter aren't showing, just in the center gutter. Any suggestions?
I think that if you check on Flatworker there's somewhere a setting which tells whether certain marks a placed on top of other layers. I think what is happening here is that in your center gutter there is space where no other objet is (as you know objects can have larger size than their visible size) but in your gutter some other object might be placed on top of the marks.
I do recall having a similar problem which was solved by using different settings.