Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2d20c93c5b9bab4f5387778b5c8a742e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563