Yes, I flew NW on the very first trip of the year basically in the same situation as you. I tried to update it on the NW website, it took it but wouldn't stay. I tried to put it in the NW kiosk on check-in and Delta wasn't an option at that time. I had to give it to an agent. On the return, when I gave my PM card to the agent for entry after using the kiosk, he then placed a priority tag on my bag.