Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/4de687f5af287e1803cdea6332e7a5a1.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563