Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a3ea1e7afc1915bb819b3093fe1f54e5.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563