I had the same issue.. Raven's solution was the last part of the jigsaw..
Here's what I set..
In Options > Special > Cyclic Trim Type - "Instant"
in Options > Miscellaneous - Unticked the "Force Feedback".. as my stick is not FFB
in controls for both Pilot and also Copilot I bind the "Force Trim - Interrupt" button to whatever you please..
The trim then worked!!..
For me it was having the FFB checked that was the last part of the puzzle to get it working
Obviously, the Force Trim needs to be ON in the cockpit.. but does by default on an Auto Start-up..
Many thanks Raven.. sorted..