Settings Page Undefined Error

I'm getting this error all of the sudden. I didn't change anything in the code for this page - but this just appeared this morning -

Fatal error: Call to undefined method MB_Settings_Page_Meta_Box::get_class_name() in /Users/silvabook/Documents/Sites/emilybennington.local/wp-content/plugins/mb-settings-page/inc/settings-page-meta-box.php on line 99

<?php

add_filter( 'mb_settings_pages', 'prefix_settings_pages' );
function prefix_settings_pages( $settings_pages )
{
	$settings_pages[] = array(
		'id'            => 'social-options',
		'option_name'   => 'social_options',
		'menu_title'    => __( 'Social Options', 'textdomain' ),
		'icon_url'      => 'dashicons-images-alt',
		'submenu_title' => __( 'Settings', 'textdomain' ), // Note this
	);
	return $settings_pages;
}

add_filter( 'rwmb_meta_boxes', 'prefix_options_meta_boxes' );
function prefix_options_meta_boxes( $meta_boxes )
{
	$meta_boxes[] = array(
		'id'             => 'general',
		'title'          => __( 'Global Site Options', 'textdomain' ),
		'settings_pages' => 'social-options',
		'fields'         => array(
			
			// TEXT
			array(
				// Field name - Will be used as label
				'name'  => __( 'Facebook Link', 'rwmb' ),
				// Field ID, i.e. the meta key
				'id'    => "facebook_link",
				// Field description (optional)
				'desc'  => __( 'Ex: http://facebook.com/your_user_name', 'rwmb' ),
				'type'  => 'text',
				// Default value (optional)
				'std'   => __( '', 'rwmb' ),
				// CLONES: Add to make the field cloneable (i.e. have multiple value)
				'clone' => false,
			),

			// TEXT
			array(
				// Field name - Will be used as label
				'name'  => __( 'Twitter Link', 'rwmb' ),
				// Field ID, i.e. the meta key
				'id'    => "twitter_link",
				// Field description (optional)
				'desc'  => __( 'Ex: http://facebook.com/your_user_name', 'rwmb' ),
				'type'  => 'text',
				// Default value (optional)
				'std'   => __( '', 'rwmb' ),
				// CLONES: Add to make the field cloneable (i.e. have multiple value)
				'clone' => false,
			),

			// TEXT
			array(
				// Field name - Will be used as label
				'name'  => __( 'Youtube Link', 'rwmb' ),
				// Field ID, i.e. the meta key
				'id'    => "youtube_link",
				// Field description (optional)
				'desc'  => __( 'Ex: http://facebook.com/your_user_name', 'rwmb' ),
				'type'  => 'text',
				// Default value (optional)
				'std'   => __( '', 'rwmb' ),
				// CLONES: Add to make the field cloneable (i.e. have multiple value)
				'clone' => false,
			),

			// TEXT
			array(
				// Field name - Will be used as label
				'name'  => __( 'Instagram Link', 'rwmb' ),
				// Field ID, i.e. the meta key
				'id'    => "instagram_link",
				// Field description (optional)
				'desc'  => __( 'Ex: http://facebook.com/your_user_name', 'rwmb' ),
				'type'  => 'text',
				// Default value (optional)
				'std'   => __( '', 'rwmb' ),
				// CLONES: Add to make the field cloneable (i.e. have multiple value)
				'clone' => false,
			),

			// TEXT
			array(
				// Field name - Will be used as label
				'name'  => __( 'Linked In Link', 'rwmb' ),
				// Field ID, i.e. the meta key
				'id'    => "linkedin_link",
				// Field description (optional)
				'desc'  => __( 'Ex: http://linkedin.com/your_user_name', 'rwmb' ),
				'type'  => 'text',
				// Default value (optional)
				'std'   => __( '', 'rwmb' ),
				// CLONES: Add to make the field cloneable (i.e. have multiple value)
				'clone' => false,
			),

			// TEXT
			array(
				// Field name - Will be used as label
				'name'  => __( 'Email Address', 'rwmb' ),
				// Field ID, i.e. the meta key
				'id'    => "mailto_link",
				// Field description (optional)
				'desc'  => __( 'Ex: [email protected]', 'rwmb' ),
				'type'  => 'text',
				// Default value (optional)
				'std'   => __( '', 'rwmb' ),
				// CLONES: Add to make the field cloneable (i.e. have multiple value)
				'clone' => false,
			),
		),
	);
	return $meta_boxes;
}
?>