Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0c4f9236dcc63a91fb86da67a7cf7e87.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563