Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/c1f1d6e1f3d9aa6e17e410b00a868acf.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563