Adding Friction to the Cyclic is also a "Must". On the Sperry system there is a preset minimum Friction.
A question....in ATT Mode....did the two trim wheels get a reaction when moved back and forth? Did the Turn Knob....push and turn....left and right...get a reaction?
When the system is operating correctly in ATT mode...you can "fly" the machine with those control "Wheels" and Turn Knob.
Force Trim must be on as I recall.....and Trim Release not depressed.
The Attitude Reference can be re-set by means of the Force Trim Release and moving the Cyclic to the desired position....and re-engaging the Force Trim by letting go of the Force Trim Release Button.
As indicated by others....the SCAS will "hold" a selected Attitude with minor adjustments being made with the two Trim Wheels and Turns being made by use of the Turn Knob. Major changes in Attitude Reference requires the use of the Cyclic and Force Trim Release.