Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a2686dfdbca897d3c9e64f4bc8292202.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563