In HH, the steady ON LED indicates that the rudder command from the TX is equal to the rudder command the gyro "learned" during initialization. Obviously, if the TX command is NOT the same as the "learned" command ... the LED will blink.

This is normal if: You are moving the rudder stick to fly the heli as long as when you recenter the stick ... the LED goes steady ON again.

This is not normal if: You center the rudder stick and it still blinks. This means that when you give a 0 YAW rate command (centered stick) ... the gyro will be getting a YAW rate command (tail will not hold). You can get this "centered" blink if you change the rudder trim setting AFTER the gyro has "learned" a different setting.

If for any reason, you need to change the rudder trim setting (AFTER gyro initialization), the gyro needs to re-learn the new setting (re-initialized or do the 3 mode change toggle step).
Since you have to power up the gyro in HH, this sequence needs to be followed:
*In HH mode, Power up/gyro initializes, learns the rudder command.
*Switch to RATE mode ... mechanically/electronically trim the heli.
*Switch to HH mode and re-init the gyro ... either by the 3 mode change toggle method or power off gyro and power back on.

Now ... in HH and stick centered, you should be trimmed and the gyro is providing 0 YAW rate control. Again ... if you have to click the trim after this ... you gotta do the re-init thing again.