Can't add routine to calender

Is anyone else having the issue where they can't add one of their custom routines to their calendar. I have a routine for boxing which I add to my calendar so it is basically running all the time. The "add to calendar" button has disappeared when I click on it for some reason. I can see the button if I create a new routine but for ones I have already completed it has gone? I don't know if I'm just confused or if something has gone wrong.