Upgraded to 3.4.2 and calendar interface disappeared

First off, I’m an office worker, not a web developer, so please forgive my ignorance of these matters.

I inherited a website to which I make minor updates and changes. Last week, I needed to upload something to my website, and Word Press suggested that for best results, I should upgrade to V 3.4.2.

Unfortunately, after doing so, the WordPress function that allows me to update my events calendar disappeared from my dashboard. This was a simple interface I would access via an “Update Calendar” button at the top of my dashboard. It would allow me to pick a date from a pull-down menu and enter an event title and description. The title would appear on our website’s calendar page, and you could click on an event title and open another page with the full event description.

The calendar on my website is still intact, https://macenter.org/?page_id=16 . What I’ve lost the ability to make any changes to it. I think the foundation functionality must still be working there somewhere, but I don’t know how to access it.

If I view the calendar page on the dashboard, it shows information for Dec. 2009 only, yet the website displays the current month & year, and all event links seem to work.

The only plugins on my dashboard are Askimet (deactivated) and Contact Form 7. I uploaded Event Manager 1.0 by Ramoonus, thinking that might be what was missing, but it didn’t help, so I deactivated it.

Does anyone know how I can get this interface back?

Thanks.