Have made apt private by mistake in shared calendar. Can I undo .
 

I have 2 problems. One, when I print calendar in monthly style it is not
printing all appointments if there is more than 2 in one day. I thought it
was because there was conflicting appointments - although they should still
have printed off. I then while looking at why this was happening
inadvertently changed one appointment to private. As this is my boss's
calender, I have shared access, is there anyway I can undo this? I made it
private but it won't let me back to change it.