Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2c19284b02ef9bdb8da9c0e7d8ae7d0f.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563