Page editor and WPMU dev won't load

Hello - I cloned an old site (vivacious onto a new domain - Someone else built the old site. The upfront editor was not loading on either site. The old developer disabled a Mailchimp plugin on the old site, which allowed the editor to load. When I disable that plugin on the new site, the editor still won't load. Any ideas what is going on?

Also I just noticed that the WPMU dev dashboard is not loading on either site, though the plugin is activated.