I cannot display events in eM Client Calendar. And when I try to create an event, I have an error message: Item saving Failed, Unable to save the item, because the account is read only.
Make sure that the calendar you are trying to save the event to is not read only. You can select a different calendar at the bottom left of the event window by clicking on the calendar name.
With not being able to display events, it may be that your calendar is somehow corrupt. You can remove the account from eM Client, then add it again. That might help.