Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/286c7a108c3095b3f8a3c2a0fc17a8f8.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563