Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/9b4868258c3750d50f142ec1f4c4e8ca.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563