No "Set Default Calendar" option

LONG story, but we had to change my wife's Apple ID. That's done, but since then, she can't edit the shared calendar that has been set up.

When I go to Settings... Calendar... there's no option to set a default calendar.

She can see the calendar, but can't add to it. She's set up to add/edit for the calendar, but it won't let her do anything but read it.

Thoughts???