Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3f376b5b71d63f58367e96a826a8c8a3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563