Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/c03f18a2c7111d3b3ca131e9792c2281.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563