Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8f25b7c9f0a9556942a3648132a9bd48.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563