Client can’t publish drafts (“This Page Isn’t Working”), but it’s working for me

Hello.
I’ve created a website for a client, and it seems like the client is not able to publish new posts. When she clicks the “Publish” button, it’s loading and loading and then gives the “This Page Isn’t Working” error. However, when I’m doing the same exact thing on my computer, everything works great.

I’ve looked for an “Error_log” file, but I only found one inside the “wp-admin” folder, and those were old errors.

Any ideas what could cause such a problem?

Thanks for any help!

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