Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/6d4a4f75f35943ba444c73f9e5a26461.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563