Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f1b42377e0093d5db2f0c59d4de7a447.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563