Cannot add any events or update new ones

Hello, I cannot create any events or update existing ones. If I try, I get a message like this one: “The site is experiencing technical difficulties. Please check your site admin email inbox for instructions.”
The only thing I can think of, is that yesterday I added a plugin called Autoptimize to speed up the website. I have since removed it from my site, but your plugin is still not working. Again, I cannot create any events or even update existing events.

The page I need help with: [log in to see the link]