Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/afc7dd07e254e484078009ff98f9d0f2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563