>Do I need to make any chances in the WordPress settings?
no, you need to look at your server error logfiles
as it says “Internal Server Error” (which could be anything and probably/possibly not a php error)

from what i recall – though i might be wrong – it had something to do with your admin ajax .php
btw, the other errors you sent me where only relevant when installing the plugin

i.e the plugin (tries) to install/add some demo images . however, as your server has http wrappers disabled it does not allow to add these images from a remote – read http:// – url so the images do not get added.

as you are unlikely to be using those images anyway, this is not an issue and does not impact anything else as this is only something that may occur on first install and has no bearing on the functionality or ability to do everything else

admin-ajax.php affects absolutely everything, everywhere
as i recall it threw a 500 error…..so pretty much no ajax request will work until this is fixed