Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/49eff7617398fe8e58c4f2a8e63c0df7.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563