I have a new install of JA Simpli and when I click on the Media Menu item to upload images in the backend, I get an error; "Property 'mime_type' of argument 'item' of event onFetchMediaItems has a wrong item. Valid: string"
Hi
You will need to enable fileinfo PHP extension on your server side
https://issues.joomla.org/tracker/joomla-cms/37052