Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0bee28f9128a0465efb1d651f0f6b4e2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563