I worked on this case few hours to come up with a new idea.

Store the level of the output after you opened:

private $ob_level = -1;

/**
 * Activate output buffer
 *
 * @since    1.0
 */
public function activate_buffer() {
	// activate output buffer
	ob_start();

	$this->ob_level = ob_get_level();
}

Get the contents of the buffer.
Then clean the buffer, which means you will have an empty buffer.

public function include_contact_bar() {
	if ( $this->is_login_page() or is_admin() ) {
		return;
	}
	// correct link target for some links if desired
	if ( isset( $this->stored_settings[ 'open_new_window_social_only' ] ) and 1 == $this->stored_settings[ 'open_new_window_social_only' ] ) {
		$contact_target = '';
	} else {
		$contact_target = $this->link_target;
	}
	// get current buffer content and clean buffer
	$content = ob_get_contents();
	ob_clean();

	// esc_url() should be used on all URLs, including those in the 'src' and 'href' attributes of an HTML element.
	// open the bar
	$inject = '<div id="scb-wrapper"';

When you echo the $content, you fill up the buffer again. And if the stored ->ob_level is equal to the current ob_get_level(), then you flush and close the buffer. (If the level is not equal, you can be sure that you are not the one who opened it.)

	}

	// display it
	echo $content;

	if($this->ob_level != -1 && $this->ob_level == ob_get_level()) {
          ob_end_flush();
      }
}

Thanks @hinjiriyo, I will be able to check it after the next week as I’m on holiday.

@cpufix2017: It would help if you could list all your activated plugins and the name of your theme. Probably one of them closes the buffer or skips the template_redirect action.

@hinjiriyo: to prevent @cpufix2017 error (his will result that your plugin won’t place the bar, but there won’t be an error message)

public function include_contact_bar() {
if ( ob_get_level() == 0) {
  // there is no opened output buffer what we could use
  return false;
}

@hinjiriyo: If I would be in your place, I would probably leave output buffers for this plugin. I would insert the HTML code into the wp_footer action and place it to the start of the body tag with JavaScript. Or wp_head with json encoded html and insert the code to the right place with JS.

• This reply was modified 11 months ago by  Nextendweb.

@cpufix2017: It is a community driven support forum and anyone can help anyone, I just tried to help you. Of course it does not mean that you can’t wait for the developer to respond.