If you didn’t see anything in the log you might need to enable higher level of logging/debugging in WP. It’s fairly straightforward – just edit the wp-config.php file. Here is what I use in my test boxes:
/** Debug */
define( 'WP_DEBUG', true ); // turn on debug mode
define( 'WP_DEBUG_LOG', true ); // log to wp-content/debug.log
define( 'WP_DEBUG_DISPLAY', false); // don't force display_errors to on
@ini_set('log_errors',1); // enable or disable php error logging (use 'On' or 'Off')
@ini_set('display_errors',0); // enable or disable public display of errors (use 'On' or 'Off')
You can find other ways of doing it if you google it online.
This will create debug.log in your wp-content directory and once you try to refresh the page with the widget you should see some kind of notice or error message that would help us get to the bottom of this.