Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/732e0a2519d07e7f3e868b4c7e6b4fef.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563