I installed eM client on a windows 7 computer and Calendar does not show up in the left colume. Mail, Tasks, and Contacts are there for my Gmail account. I just bought a Windows 10 laptop and it does show Calendar for the Gmail account.
sounds like you accidentally hid the Calendar item.
Just right click any of the other items and a drop-down menu with all menu possibilities should pop up. Just check the Calendar again.
I found your answer to someone else’s problem with the Calendar disappearing.
Thank you! That was exactly what had happened on my eMail Client. I’m so grateful to have my calendar back!