Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ba29a0f76e67d5a3d5f2dd34dc7a578f.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563