Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/aa402589a9e4a88f5d26689298bc5f76.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563