Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/6ebf1553fee15bf4c3a9f3240263a7f4.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563