if you are using reloaded rounds that have NOT been properly full length sized for correct headspace, the case could be too long from base to shoulder. this will not let the encore action lock up correctly and will prevent the hammer from cocking.
if this is the case, you would need to adjust your full length size die to bump the shoulder back.
if you neck sized only, you may need to try full length sizing.
also, if you are not properly lubing the insides of the neck during resizing, you could be pulling the shoulder back out when dragging the expander back thru.
i have done all of the above in my learning process. :wink: