To print the Nav Log, click on the Nav Log button that is at the bottom of the Route window on the far left of the screen. That should open the navigation log and allow you to print it directly from that screen.
If you are trying to print the actual flight plan form (FAA 7233-4), click on the File button at the bottom of the same Route window. When the File window opens, click the Print Form button at the bottom of the window to open the FAA 7233-4 form and print from that window.
If this is not working for you or you need further assistance, please submit a support ticket or, contact our technical specialist via phone for assistance:
AOPA Flight Planning Products Team
Customer support service by UserEcho