Usually a white page means a php error. You will probably need to turn on the display of php errors or look in the php error logs. that will give you a clue as to what is going on. After that check out the troubleshooting section of the grav learn site.
how can i see the php errors in file zilla?
You need to enable display of php errors. Look here for more information: http://stackoverflow.com/questions/1053424/how-do-i-get-php-errors-to-display
there are no errors… can’t the host be the problem?
can you drop a file called info.php with this content into your directory:
<? phpinfo();
This will at least tell you the version of PHP and what core modules are installed.