Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/11993f99da1f19e026ded807ade6c2e3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563