@Jeanne – interesting, can you try turning on WP DEBUG and see if any errors come up?: https://codex.wordpress.org/WP_DEBUG
@Giovanni – same as above, can you try increasing your PHP memory limit? If that doesn’t work, try turning on WP DEBUG and let me know if any errors come up.
If nothing shows up, I may need to be able to access your site using a temporary admin login so I can debug further.
Let me know 🙂