Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/e5adb5672ce93dac6d6f4d5ed9bc6736.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563