Notice: wp_enqueue_style was called incorrectly. Scripts and styles should not be registered or enqueued until the wp_enqueue_scripts, admin_enqueue_scripts, or login_enqueue_scripts hooks. Please see Debugging in WordPress for more information
This notice is not very helpful in tracking down the actual code causing the problem. Most solutions suggest deactivating all your plugins and switching to the default theme and then slowly reactivate each one until you find the problem. Who has time for that? Just install the Query Monitor plugin. Once the error shows go to the PHP Errors tab, expand the Location section and you’ll get a trace on the calling plugin. In my case this was the Slimbox plugin which fortunately I wasn’t using.