I want to write a custom plugin that does some action after woocommerce order is completed, but I can\'t get this hook to work. I can see this question asked many times.
Try using action hook woocommerce_order_status_changed. It takes 4 parameters. order id, old status new status and order. Further code reference HERE
woocommerce_order_status_changed
This may not be exactly suitable to your requirement, but seems to be worth of an alternative. Hope this helps.