I have received a request to join an icloud calendar. When I go to the calendar inbox to accept, the window closes and nothing happens. The notification remains and I do not have access to the calendar...

Howdy gbkurschat,

It sounds like you are trying to accept a calendar invite on your iIS device but the app keeps closing on you. I would quit the Calendar app, and the Settings app:

iOS: Force an app to close

Double-click the Home button.

Swipe left or right until you have located the app you wish to close.

Swipe the app up to close it.

When you have done that restart the device and test the issue again:

iOS: Turning off and on (restarting) and resetting

Thank you for using Apple Support Communities.

Take care,

Sterling