Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/de45e7d01a6d4d3f2ac8c995e62d3028.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563