Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f4cc993aec394f58b071f0c090c0e3c7.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563