Try to open \applications\featuredcontent\widgets\fcontentWidget.php
Find
$form->add( new \IPS\Helpers\Form\Select( 'sliderID_to_show', isset( $this->configuration['sliderID_to_show'] ) ? $this->configuration['sliderID_to_show'] : 0, TRUE, array( 'options' => $options, 'parse' => 'normal' ) ) );
Replace by
$form->add( new \IPS\Helpers\Form\Select( 'sliderID_to_show', isset( $this->configuration['sliderID_to_show'] ) ? intval( $this->configuration['sliderID_to_show'] ) : 0, TRUE, array( 'options' => $options, 'parse' => 'normal' ) ) );
Save
I see the issue slider can not be shown because all images have dead links.
Try to use this cimage version
https://invisionpower.com/applications/core/interface/file/attachment.php?id=71715
Or config your cimage to allow external url.