Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/811135e4ca3dbf5524f49174c07f9b68.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563