Fatal Error

PHP Fatal error:  Uncaught TypeError: base64_decode(): Argument #1 ($string) must be of type string, array given in /var/www/html/wp-content/plugins/custom-facebook-feed/inc/SB_Facebook_Data_Encryption.php:99
Stack trace:
#0 /var/www/html/wp-content/plugins/custom-facebook-feed/inc/SB_Facebook_Data_Encryption.php(99): base64_decode(Array, true)
#1 /var/www/html/wp-content/plugins/custom-facebook-feed/inc/CFF_Shortcode.php(1846): CustomFacebookFeed\SB_Facebook_Data_Encryption->decrypt(Array)
#2 /var/www/html/wp-content/plugins/custom-facebook-feed/inc/CFF_Shortcode.php(298): CustomFacebookFeed\CFF_Shortcode->get_settings_for_feed(Array)
#3 /var/www/html/wp-includes/shortcodes.php(356): CustomFacebookFeed\CFF_Shortcode->display_cff('', '', 'custom-facebook...')
#4 [internal function]: do_shortcode_tag(Array)
#5 /var/www/html/wp-includes/shortcodes.php(228): preg_replace_callback('/\\[(\\[?)(custom...', 'do_shortcode_ta...', '[custom-faceboo...')
#6 /var/www/html/wp-includes/class-wp-hook.php(309): do_shortcode('[custom-faceboo...')
#7 /var/www/html/wp-includes/plugin.php(189): WP_Hook->apply_filters('[custom-faceboo...', Array)
#8 /var/www/html/wp-includes/widgets/class-wp-widget-text.php(281): apply_filters('widget_text', '[custom-faceboo...', Array, Object(WP_Widget_Text))
#9 /var/www/html/wp-includes/class-wp-widget.php(393): WP_Widget_Text->widget(Array, Array)
#10 /var/www/html/wp-includes/widgets.php(2022): WP_Widget->display_callback(Array, Array)
#11 /var/www/html/wp-includes/rest-api/endpoints/class-wp-rest-widgets-controller.php(697): wp_render_widget('text-2', 'primary')
#12 /var/www/html/wp-includes/rest-api/endpoints/class-wp-rest-widgets-controller.php(154): WP_REST_Widgets_Controller->prepare_item_for_response(Array, Object(WP_REST_Request))
#13 /var/www/html/wp-includes/rest-api/class-wp-rest-server.php(1141): WP_REST_Widgets_Controller->get_items(Object(WP_REST_Request))
#14 /var/www/html/wp-includes/rest-api/class-wp-rest-server.php(988): WP_REST_Server->respond_to_request(Object(WP_REST_Request), '/wp/v2/widgets', Array, NULL)
#15 /var/www/html/wp-includes/rest-api.php(511): WP_REST_Server->dispatch(Object(WP_REST_Request))
#16 /var/www/html/wp-includes/rest-api.php(2860): rest_do_request(Object(WP_REST_Request))
#17 [internal function]: rest_preload_api_request(Array, '/wp/v2/widgets?...')
#18 /var/www/html/wp-includes/block-editor.php(501): array_reduce(Array, 'rest_preload_ap...', Array)
#19 /var/www/html/wp-admin/widgets-form-blocks.php(25): block_editor_rest_api_preload(Array, Object(WP_Block_Editor_Context))
#20 /var/www/html/wp-admin/widgets.php(32): require('/var/www/html/w...')
#21 {main}
  thrown in /var/www/html/wp-content/plugins/custom-facebook-feed/inc/SB_Facebook_Data_Encryption.php on line 99